An awful lot of American liberals have become rather possessed by the possibility that President Trump is somehow in league with Russian President Vladimir Putin. The circumstantial evidence that there is some sort of connection is rather strong — Putin very probably helped Trump win in 2016, some Trump associates have a rat's nest of connections with Russia, and Trump himself has been relying on financing from Eastern Europe for many years.

But definitive proof has yet to surface. So in their quest to find a connection — particularly some sort of direct conspiracy between Trump and Putin — some liberals are abandoning good sense and becoming credulous toward nutty thinkers.

It's important to avoid this not only because clear thinking is important, but because it is the best way to root out the truth.

I'm reminded in a way of the Second Red Scare. The era of Joseph McCarthy is rightly remembered as a time of deranged witch hunts and fevered anti-Communist paranoia. Something that is a bit less remembered is that the Soviet Union did indeed have extensive espionage success within the American government, particularly during the Second World War. They penetrated the Manhattan Project, they scooped up all manner of non-nuclear weapons technology, they recruited one of the very top economic policy officials in the country, and on and on.

In other words, the defining characteristic of McCarthyism was not a false belief that KGB spies had infiltrated the government, because they had. It was paranoia and hysterical panic about such spying, especially in how it was used to further partisan Republican ends. McCarthy was a fool and an incompetent drunk, but other Republican elites tolerated him and his accusations because he whipped up unhinged outrage against Democratic Party elites and policies. They loved it when he was falsely smearing Dean Acheson and George Marshall as secret Soviet sympathizers, or slagging public housing bills as the first step to Communism. It was only when McCarthy's erratic, diseased thinking, his constant lying and fabrication, and his utter investigative incompetence became undeniable that they began to desert him.

A corollary of this is that McCarthy was an active impediment to anti-espionage efforts. During the Red Scare, it's possible his various lists of supposed Communists included a small fraction of actual Soviet spies. But what tiny truth was there was swamped by the huge number of innocents caught up in the panic. What's more, after McCarthy's downfall the whole idea of Soviet infiltration of the American government was badly tainted by association with his vile methods.

(As an aside, it's important to note that all of this is orthogonal to the question of whether Soviet spying necessitated a hyper-belligerent diplomatic stance towards the USSR. All countries spy, America very much included, and in the end all the espionage probably didn't amount to much — indeed, it may have actually calmed tensions somewhat.)

Now, liberals' Trump-Russia fever is not remotely as bad as what struck Republicans during the McCarthy era. There is no full-blown panic, nor any show trials. Yet there is an echo of the basic mechanics. Instead of a Wisconsin senator, we have Louise Mensch, a former Conservative MP and bug-eyed conspiracy hound who has been all over cable news making one unsubstantiated accusation after another — and even somehow got a piece in The New York Times. And she is only the most prominent of a cottage industry of instant Russia "experts" who have sprung up to write long tweet threads and create infographics in Microsoft Paint validating liberals' darkest suspicions about Trump.

Again, it's important to emphasize, it really is possible Putin and Trump did collude somehow, or had some other connection. Liberals are right to smell blood in the water, and as I've argued before, it's only right and proper for a full investigation to be conducted. Ideally Congress would serve its constitutional duty, but with Republicans on the House Intelligence Committee, especially Chairman Devin Nunes, giving every sign of working hand-in-glove with the Trump administration to quash the ongoing investigation, that route may be closed off for the time being.

In the meantime, outside investigations and journalism are all that we have. But it's still critical for liberals to maintain a grip on reason, and require proof for extraordinary accusations. Even if Democrats manage to take back the House in 2018 and mount a true investigation, they can't assume that a smoking gun — particularly one proving direct Trump-Putin collusion — will be found.

In the meantime, there are plenty of horribly unpopular things Trump is doing, and horribly unpopular policies his party supports, to use as political weapons.