Alternative to "queer the deal"?

As a bonafide queer person myself, I've never even heard this particular turn of phrase.

I would either use jinx, as Glorfindel suggests, or potentially curse or hex as all of those terms explicitly evoke the superstitious nature that you were looking for. I do think jinx is the most common, however.

Examples:

Mom: Oh, you're done with your degree, congratulations!

Me: Don't say that yet, you'll curse me!

In my case, I was fully aware that odds were very good that I would graduate (and I did!), but the illogical part of my brain was convinced that if anyone congratulated me on it, I would fail.

The answer by Glorfindel identifies "jinx" as a very good option, which I agree with for the "superstition" meaning; it seems to substitute well in the form "jinx it", such as "I don't want to jinx it". However, I don't think it's appropriate for more material concerns over what you call "mental poise".

The most appropriate word I can think of for that meaning is "choke", using the intransitive verb definition 4 from here:

to lose one's composure and fail to perform effectively in a critical situation

Alternatively, if you really need a single word or phrase that mixes superstition with mental poise, the closest I can think of is "psych out" with usage something like "I don't want to psych myself out." It can be used to express this kind of sentiment: "I don't want to worry about a superstition because doing so would upset my mental poise and cause me to fail." This is somewhat tenuous and it would be clearer if you specifically mentioned superstition as well, but I don't know of anything closer.

To reiterate, I don't think a single phrase perfectly aligns, but these each can apply to some of the situations:

• If you want to avoid a superstition, "I don't want to jinx it."
• If you want to preserve your mental poise, "I don't want to choke."
• If you want to preserve your mental poise by avoiding a superstition, "I don't want to psych myself out thinking about it." (With "it" being the superstition.)

It sounds like you want to use classical meaning of "queer" not because it is the most "Simple English correct" term, but to add color and dimension to your language. Any of a huge variety of slang terms for "breaking it" will suffice.

Don't scotch the deal

Don't flub the deal

Don't zorch the deal

Don't botch the deal

Really, that list is pretty endless.

You can also throw a little "Darmok & Jilad at Tenagra" (or more precisely, "Shaka, when the walls fell") in there, by adapting a cultural reference- someone who "snatched defeat from the jaws of victory", facepalmed, or let loose lips sink ships. That's trickier, and subject to context. "don't Kee Bird the deal" would play among airplane restorationists.

The Jewish or Yiddish word "Kinehora" might work. To my untutored ear it sounds like "KAN - UH - HARA." I hear Americans including my wife's Jewish family say it. It means don't jinx it by anticipating it before it's completed.

For example, " Five years and my Ph.D. is almost complete, only weeks to go!" Or celebrating an offer of work or a deal before the contract is signed. People then say, "Don't put a kinehora on it."

Here's a reference: http://www.jewishanswers.org/ask-the-rabbi-category/miscellaneous/?p=1855

It is related to the panoply of expressions for which queer is used, comprising various markers - often derogatory, some of them such as the association with homosexuality now considered offensive. Another is the British expression queer street, slang for bankruptcy. (A bankrupt person or business is said to be "in queer street".)

As well as noun and adjectival senses of queer,however, two verb senses have entries in the OED. The first is derived from inquire or query and has no relevance here.

However the second, especially sense 2b is exactly relevant to this question.

b. to queer the pitch: (originally) to interfere with or spoil the business of a street vendor or performer (cf. pitch n.2 17a); (later more generally) to interfere with or spoil the business in hand; similarly to queer a person's pitch. Also in similar phrases, as to queer the game, to queer the deal, etc.

1846 ‘Lord Chief Baron’ Swell's Night Guide (new ed.) 47 Rule iv... Nanty coming it on a pall, or wid cracking to queer a pitch. 1866 M. Mackintosh Stage Reminisc. vii. 93 The smoke and fumes of ‘blue fire’ which had been used to illuminate the fight came up through the chinks of the stage, fit to choke a dozen Macbeths, and—pardon the little bit of professional slang—poor Jamie's ‘pitch’ was ‘queered’ with a vengeance. 1875 T. Frost Circus Life xvi. 278
The spot they select for their performance is their ‘pitch’, and any interruption of their feats, such as an accident, or the interference of a policeman, is said to ‘queer the pitch’. 1889 E. Sampson Tales of Fancy 38 They could not understand it when their pitch was queered, and one or two of the gang arrested. 1901 Windsor Mag. Dec. 204/1 I think you and I between us have queered the game. 1912
Chambers's Jrnl. Dec. 795/2 All branches of the administration work sensibly and effectively so long as you do not ‘queer the pitch’ by creating exceptions. 1973 E. Lemarchand Let or Hindrance iv. 31
He's a decent lad... He would never have risked queering Wendy's pitch with Eddy. 1993 Chicago Tribune 19 June i. 14/2 This presumes..that Nolan doesn't queer the deal by holding more press conferences to warn how crime-ridden Chicago will become. 2006 Econ. Times (India) (Nexis) 4 Oct. What queers the pitch for the airlines is the additional capacity entering the domestic market over the next three

Queering the deal means to have some (usually last minute) new condition or circumstance to contend with, which threatens the delicate balance of (a perhaps not altogether above-board) negotiated arrangement. Last minute demands of facilitators who want to increase their cut of the deal are typical examples. The ability to queer a deal is the essence of pork barrel politics. The phrase was established by 1900.

"A good cigar," said the dealer, "and you can have it now if you want it." The coachman was wrath. Whenever his employer purchased a horse, he said he had always gotten a "rake off" of $25 from the dealer and he now demanded $75 as his commission for inducing his employer to buy an automobile. If money wasn't forthcoming, he declared he would "queer the deal."

The Horseless Age: The Automobile Trade Magazine, Volume 8, 1901.

So the alternatives should preserve this sense of meddlesomeness.

The first that comes to mind is "scotch the deal", but I rather think this doesn't solve the problem so much as impune the Scots. However it is surviving in the news just fine, at least in British news. Scotch the deal generally implies somebody benefits from the deal not happening at all, while queer the deal is normally used where all parties need some sort of deal to go through to benefit.

"Stymie the deal" is close and has some currency.

In handing down his ruling, federal judge Richard Leon said the Justice Department -- whose antitrust chief, Makan Delrahim, brought the rare case -- failed to provide sufficient proof that the deal would harm competition or consumers. He also warned the U.S. government against bringing an appeal if the purpose was to try to stymie the deal, though the DOJ has not indicated its next steps.

AT&T-Time Warner merger approved, setting stage for more consolidation, Daily Herald, 6/13/2018. https://www.dailyherald.com/business/20180612/att-time-warner-merger-approved-setting-stage-for-more-consolidation

"Muddle the deal" seems like a good option.

While the Reynolds-Lorillard deal shakes up the lucrative but slowing U.S. market, it doesn't alter the global picture dramatically. That makes it unlikely Philip Morris, the global leader in cigarette sales excluding China, or Japan Tobacco, would feel the need to swoop in and try to muddle the deal with any counteroffer, industry watchers said.

Amid U.S. Tobacco Merger, Is the Global Deal Making Done?, The Wall Street Journal,Jul 15, 2014. https://blogs.wsj.com/moneybeat/2014/07/15/amid-u-s-tobacco-merger-is-the-global-deal-making-done/

Don't sour the deal

One of the definitions at oxforddictionaries.com is:

(verb) Make or become unpleasant, acrimonious, or difficult.
[with object] ‘a dispute soured relations between the two countries’

As I'm not superstitious, I can't comment on that meaning.

I'm flattered by OP's suggestion that only younger people today use "queer" as homosexual. I'm retired and have always understood it that way. Perhaps it's BrE that's only recently entered AmE.

The 'deal' could be considered a complicated and multi-faceted operation. For this, I would offer,

Don't throw a wrench in the works.

This instills vivid metaphoric imagery of halting the machinations of a complex transaction or process through one's actions or inactions.

I am certainly aware of the meaning of the phrase "queer the deal" but can't remember ever using it.

A bit more long-winded, but what I usually say is snatch defeat from the jaws of victory, which Collins Dictionary defines as:

phrase [VERB inflects] If someone snatches victory from the jaws of defeat, they win when it seems that they are certain to lose. If someone snatches defeat from the jaws of victory, they lose when it seems that they are certain to win.

I Don't want to throw off my groove

(alt. "mess up my groove")

This phrase was made popular by the 2000 movie The Emperor's New Groove, though the phrase it originates from ("get into a groove") predates the movie by quite a bit.

(1) The meaning of "queer the deal"

The comments have shown considerable controversy over the correct meaning of the phrase "queer the deal".

(a) Forfeiture. Can the construction be paraphrased as 'cause a deal to not go through at all?' Then adequate linguistic substitutes could be break the deal, thwart the deal.

(b) Imperil. Does the expression mean, 'do something that might threaten a deal to go through?' In this case we could think about generic alternatives, such as jeopardize the deal, or risk the deal.

(c) Superstition. Does the saying have the specific association of a superstitious fear to ruin a basically done deal last minute? If so, we might consider jinx the deal.

(d) Meddling. Is the phrase connoted with the idea of last minute meddling to increase one's cut of a deal? If this is the case, we might pick a phrase like sabotage the deal, stymie the deal.

(2) Naturally occurring examples

An investigation of naturally occurring examples of "queer the deal" can help us find out which paraphrase reflects current usage. So, I googled the construction, and randomly selected 5 examples from the results list. I did not cherry-pick or exclude examples. I then decided whether they support the forfeit, imperiling, superstitious or meddling interpretations.

Example 1:
_{Context: American novelist Jack Kerouac wrote a book. Warner Brothers offered $110k for the rights to turn it into a movie. But Kerouac's agent asked for $150k. Warner Brothers declined and the deal did not go through.}

"Kerouac was mad at his agent because he thought he had queered the deal by asking too much"
(Source: On the road again, 2005)

(a) Forfeiture: Yes, (b) Imperil: No, (c) Superstition: No, (d) Meddling: Maybe

Example 2:
_{Context: A restaurant reviewer was at a pub called "Morrissey Pub". He needed to be at another bar at 9.30pm to write a review for it. However, he did not make it to the other pub in time for the following reason:}

"[T]he bartender at the Morrissey Pub queered the deal by comping me a beer"
(Source: George Stroumboulopoulos: The Truth on TV, 2010)

(a) Forfeiture: Yes, (b) Imperil: No, (c) Superstition: No, (d) Meddling: No

Example 3:
_{Context: Blogger trying to sell their home}

"[W]e already sold this house, last Sunday. Here we are again this Sunday, ZERO showings. You see, our buyer's investor group queered the deal. So that leaves us looking for a NEW buyer.
(Source: Looking Ahead, 2018)

(a) Forfeiture: Yes, (b) Imperil: No, (c) Superstition: No, (d) Meddling: No

Example 4:
_{Context: A 1930s religious group took offence at certain liberal Hollywood movies. The religious and Hollywood agencies have negotiated a deal that still needs to be passed. Hollywood was nervous and definitely wanted to pass the deal.}

"Scared straight by Legion boycotts and New Deal threats, the members of the MPPDA Board sent instructions back to the moguls to do absolutely nothing to queer the deal. 'If Joe Breen tells you to change a picture, you do what he tells you.'"
(Source: Hollywood's Censor, 2009)

(a) Forfeiture: Maybe ('do nothing to forfeit the deal'), (b) Imperil: Maybe ('do nothing to imperil the deal') (c) Superstition: No, (d) Meddling: No

Example 5:
_{Context: The author criticizes hypocrisy in the Democratic party. There is no specific 'deal' mentioned. Rather, there is an abstract idea of pleasing voters, gaining support, becoming popular.}

"Exposure of what they [=Democrats]'re saying among themselves about what they sell to the public threatens to queer the deal."
(Source: The Liberal War on Transparency, 2012)
(a) Forfeiture: Maybe ('threatens to forfeit the deal'), (b) Imperil: Maybe ('threatens to imperil the deal') (c) Superstition: No, (d) Meddling: No

(3) Conclusions

• There is no evidence that "queer the deal" has a superstitious association in any way. Hence, to jinx the deal is not an adequate alternative. This expression conveys a fundamentally different, mental, psychological rather than factual, efficacious, conceptualization of the cause for breaking a deal.
• Likewise, I cannot see any consistent evidence for the claim that "queer the deal" somehow involves meddling, the idea of last-minute modifications for one's own benefit, or exploitative strategies. Therefore, one should not replace the expression with sabotage the deal, stymie the deal either.
• In current English, "queer the deal" seems to be used in a relatively broad, general way - it simply means 'to forfeit a deal'.

(4) Proposed Alternative

Given the most common use of "queer the deal" demonstrated above, I would propose the following PC-alternative for the expression:

to blow the deal

• The phrase "to blow the deal" has the desired meaning, a forfeiture of a deal.
• The expression "to blow the deal" already sounds quite natural and idiomatic so that it would not upset speakers too much or sound artificial.
• The expression can easily replace "queer" in all the cited examples, including the paraphrase mentioned in the question: "I'm trying not to talk about it to not upset my negotiation so don't find me rude but I'd rather not go in to details." → "I don't wanna blow the deal."
• The words "queer" and "blow" share a similar register, both being quite colloquial, informal, slangy.
• The expressions also have a similar rate of use - both are extremely rare at a frequency of c. 0.1 instances per million words.

The graph from Google Ngram viewer summarizes:

I checked three dictionaries of British idioms, and none of them has an entry for "queer the deal." However two of them do have entries for "queer someone's pitch" which WS2 raises in his answer. From John Ayto, Oxford Dictionary of English Idioms,third edition (2010):

queer someone's pitch spoil someone's chances of doing something, especially secretly or maliciously. British

This phrase originated as 19th-century slang; early examples of its use suggest that the pitch referred to is the spot where a street performer stationed themselves or the site of a market trader's stall.

[Example:] 1973 Elizabeth Lemarchand Let or Hindrance He's a decent lad....he would never have risked queering Wendy's pitch with Eddy.

And from Longman Dictionary of English Idioms (1979):

queer someone's pitch coll[oquial] to cause trouble for a person, e.g. by ruining or upsetting his plans or arrangements: it will really queer their pitch if it rains on the day of their trip to the sea Also: queer the pitch for Pitch here refers to the place, e.g. in the street or a market, where a person stands and arranges his goods for sale. Originally someone was said to queer a person's pitch if he established his pitch close by, selling the same goods

If we take "queer the deal" as meaning roughly the same thing as "queer the pitch" (or "queer someone's pitch"), then a comparable phrase might be "put the kibosh on". Here is the entry for that phrase in Christine Ammer, The American Heritage Dictionary of Idioms, second edition (2013):

put the kibosh on Restrain or check something, as in The rain put the kibosh on our beach party or The loss put the kibosh om the whole project. The word kibosh has been in English since the first half of the 1800s, but its origin is unknown.

Longman Dictionary of English Idioms has an entry for "put the kibosh on," too:

put the kibosh on coll[oquial] to spoil or prevent (a plan, idea, etc.) from happening or being successful: the rain has put the kibosh on our plans for doing some gardening this afternoon {V: Pass 1} Also (coll[oquial]) put the mockers on

...as does Ayto's Oxford Dictionary of English Idioms:

put the kibosh on put an end to; thwart the plans of. informal

The meaning and origin of kibosh is uncertain. 'Put the kye-bosk on her' is used by 'a pot-boy' in Charles Dickens's Sketches by Boz (1836).

To judge from the example sentences in which rain is said variously to "queer their pitch ... on the day of their trip to the sea" and "put the kibosh on our beach party" and "put the kibosh on our plans to do some gardening this afternoon," there is considerable overlap in the application of the two terms.

Alternative to “queer the deal”?

I'd simply suggest "sour the deal".

This is in reference to the souring of wine to vinegar in the brewing process by contamination of the brew with air.