For me I think it has to be Russiagate. It’s just become a catch all for centrist libs to refuse to believe anything bad about their team, make up crazy conspiracies about anyone to their left or right, dismiss every contradiction of capitalism as “Russian interference”. It’s maddening. At least the RWNJ conspiracies like Q and the Alex Jones shit are usually pretty funny because of how ridiculous they are, russiagate doesn’t even have that going for it.
What are some other contenders?
As with a lot of things, the right observes a very real phenomenon in their "Trump Derangement Syndrome" meme but of course apply it in the most malicious and disingenuous way possible.