I think their goto is "Russiagate" but that's because the refuse to acknowledge the facts that Mueller did have evidence but assumed that Congress would act upon it.
There is some (though in my opinion not much) merit to how right-wingers portray the "Russiagate" thing. The Russian government absolutely did try to interfere in the 2016 US presidential election to help Trump and hurt Clinton, via hacking and releasing emails and via social media influence campaigns, but there was a chunk of the left that from the start seemed to firmly believe Trump was some kind of literal espionage agent of Putin.
While it's difficult to deny Trump was a de facto asset of Putin in many ways, a surprising number of people were almost entering right-wing conspiracy theory territory with their epistemological practices regarding Trump's personal involvement with Putin.
Right-wing conspiracism is orders of magnitude worse and more frequent than left-wing conspiracism, but some people were way too willing to believe some of the more radical Russian collusion speculation despite no evidence.
I'm not the grandfather commenter, I'm very much a leftist, but left, right, there's too many whose emotions or tribalism override their logic and make them deny what they see/come up with dumbass theories.
For a left example, there are people who theorize that the guy who missed putting a bullet in Trump's brain must've been a false flag operator. Although it must be mentioned that "leftie" conspiracy theories are mostly just on social media, while "right" ones end up being broadcast by congresspeople and senators, probably because they know their side will take them at face value..
I won’t go to bat for anything near a full equivocation in contemporary politics, but it’s worth remembering antivax was heavily left-coded prior to Covid. I don’t think approximately anyone has actually good epistemology - just biases that fluctuate in how much they affect the real world. Left wing academics and outlets carrying water for people like Pol Pot in the late 20th century because they liked the idea of communism was a particularly bad one.
Even before COVID things were shifting - the antivax part of the left at that time were mostly only sort of aesthetically on the left. I think this Twitter exchange sums up my feelings about that counterargument: https://i.imgur.com/gNXJ6Wl.jpeg
Also, I think it's important to separate "left of center" and "leftist". Liberals and leftists are very different. "Progressive left-liberals" are fans of democracy and freedom and don't like bigotry and authoritarianism and Trump. "Leftists" are often fans of Lenin and Stalin and Pol Pot and killing groups of people who aren't ideologically aligned and instating one-party dictatorships and violently suppressing dissent. In leftist parlance, "leftist" = "Marxist" while "liberal" = "capitalist belonging to the moderate wing of fascism". In the US, politics is best described as not two but four factions: leftists, liberals, rightists, and neo-Nazis. Often neo-Nazis will form coalitions with the rightists to help achieve major goals; historically leftists would form coalitions with the liberals, but this seems to be occurring less and less.
Although leftists will insist the notion is absurd and anti-intellectual, horseshoe theory contains a lot of truth in it.
By left-wing politicians, basically none (while right-wing conspiracy theories are now promoted by tons of right-wing politicians). Among non-politicians: while right-wingers are far more likely to believe in conspiracy theories and the nature of the conspiracy theories they believe are far less tethered to reality on average, conspiracism is still a serious issue on the left.
It's like 50x less of an issue but I deal with so many left-wing conspiracies on a daily basis. I think the right is much worse than the left (on this topic and in general) but quite a lot of the left, or at least the populist left/populist far-left is, to me, its own particular sort of exhaustingly insufferability. I am proudly a left-liberal and not a centrist and never won't be, but I am still at a point where I can no longer tolerate a big sub-faction of the left. (Though I can't tolerate basically any of the right, minus a bit of the anti-Trump center-right.) I am going to lose my mind when I see vast numbers of leftists demand people not vote for the Democratic party presidential candidate in 2028.
