What is it about Russia — some vestige of all those Cold War spy films, perhaps — that mentioning it makes so many people, on all political sides, behave so irrationally?

Consider the behavior of Democrats who are seeking to prove that Donald Trump or his campaign "colluded" with Russia, with the implication that this "collusion" somehow determined the outcome of the 2016 election.

The mainstream media feeds this narrative with breathless multiple-bylined stories about Attorney General Jeff Sessions's casual encounter with the Russian ambassador in the Mayflower Hotel or Donald Trump Jr.'s ludicrous meeting with the Russian lady lawyer.

Of course, a genuine conspiracy would have been conducted with the Internet-age equivalent of secret messages written in invisible ink delivered to secret dropboxes. And it's not clear what useful guidance the shambolic, tweet-driven Trump campaign could have given to Russians bent on messing with the American electoral process.

In any case, the Russia issue was litigated during the campaign. Candidate Trump's weird unwillingness to say anything negative about Vladimir Putin, plus his past business dealings in Russia, raised legitimate questions about his Russia policy. Hillary Clinton intelligently and aggressively aired these issues in debate and on the stump.

No evidence has been found that any state's election system was hacked. Hackers, apparently Russian (though Trump weirdly said he doubted that), tried to access Republican and Democratic servers. They penetrated the Democrats' system and publicized embarrassing emails. Does anyone believe those stories switched the 77,000 votes by which Trump narrowly carried Pennsylvania, Michigan, and Wisconsin? Not really.

Ever since about 9:00 Eastern on election night, Democrats have been yearning to oust Trump from office. Some otherwise intelligent liberals outlined scenarios putting Hillary Clinton in the White House. Many imagine now that some smoking gun of "collusion" evidence will result in Trump's impeachment and removal from office.

But it's hard to imagine what it could be. Special prosecutor Robert Mueller may ensnare some witness in a perjury trap, but how do you have a smoking gun when there's no identifiable crime?

I think it's irrationally risky for Democrats to make "collusion" their major issue and effectively to promise they'll impeach Trump if they win a House majority next year. More to the point, House Democratic Leader Nancy Pelosi seems to agree and has told colleagues to downplay the I-word.

She doesn't want to alienate that quantum of voters willing to vote for Democrats to check Donald Trump, but not to force an impeachment trial which will, as in 1999, result in acquittal in the Senate. But such cool rationality seems rare among her fellow Democrats.

Cool rationality is not a term anyone, fan or foe, seems likely to attach to Donald Trump any time soon. His tweets and interview responses, seemingly determined to prompt Jeff Sessions's resignation as attorney general, are as irrational as critics' scenarios of his imminent replacement by Hillary Clinton.

Sessions, the only senator to endorse him before he clinched the Republican nomination in May 2016, has striven faithfully to carry out his policies. His recusal from involvement on Russia matters last March, though over-cautious in my view, was something Trump could have cautioned against then. And Trump could now legitimately call on Deputy Attorney General Rod Rosenstein to cabin in what National Review's Andrew McCarthy has argued is Mueller's illegally broad mandate. Presidents have lines of communication with appointees less public than Twitter.

Trump, of course, has only himself to blame for Mueller's appointment, which resulted from self-admitted clever leaking and maneuvering by James Comey after he was abruptly fired as FBI director in May.

Meanwhile, it's hard to dismiss as fake news reports that other cabinet members and Republican senators are dismayed and disheartened at Trump's treatment of Sessions. You would surely feel that way yourself if you were in their shoes.

Moreover, if Sessions resigns or is fired, there will be confirmation hearings for his replacement. One thing Democrats and maybe some Republicans will demand is a commitment that Mueller not be fired or his investigation limited.

Similar commitments extracted from Attorney General Elliot Richardson and Deputy Attorney General William Ruckelshaus prompted their resignations when Richard Nixon ordered them to fire special prosecutor Archibald Cox in October 1973. Nixon resigned 10 months later.

It has long been my contention that the political marketplace, like the economic marketplace, operates tolerably well when competitors, constrained by the rule of law, act out of rational self-interest.

It doesn't work so well when, as today, people on both sides keep acting irrationally.