Technically, collusion isn't a crime. There is no statutory definition of "collusion"; the closest we could come is "conspiracy." So let's be more specific: Would it be criminal activity if the Trump campaign solicited opposition research from the Russian government? The short answer: Not clearly, unless the campaign was also involved in underlying criminal activity, such as hacking the Democratic National Committee or the Hillary Clinton campaign.
UCLA professor of law Eugene Volokh explained in the Washington Post last year that barring such activity, it seems violative of the First Amendment to prevent campaigns from talking with foreign citizens about opposition research on other candidates.
After all, Clinton's team paid Fusion GPS to create an opposition-research dossier, much of the material provided by a foreign citizen, Christopher Steele. Even exchanging information with the Russian government wouldn't clearly violate the law, if Volokh is correct.
Now, this doesn't mean that the Trump campaign is in the clear. It just means that Trump's opponents will have to prove far more than they've proved so far.
All of which means that the slim hook on which the Democratic hopes of a Trump criminal charge are based grows even more tenuous. Now Democrats are banking on the possibility of an obstruction charge emerging against Trump: perhaps, they say, Trump has attempted to shut down special counsel Robert Mueller's investigation in some way.
After all, he's constantly tweeting about the myriad evils of the so-called "witch hunt."
But even here, the statutory basis for such a charge is thin: There are provisions covering destruction of evidence or threatening to influence a "pending judicial proceeding," but obstruction generally requires an active attempt to impede â€” and the Mueller investigation, according to the testimony of Deputy Attorney General Rod Rosenstein, hasn't actually been impacted by Trump's fulmination.
The best hope for Democrats is a perjury charge against Donald Trump Jr. They hope that Trump Jr. lied when he said that his father didn't know about the June 2016 Trump Tower meeting with Russian lawyer Natalia Veselnitskaya; perhaps, they think, they can charge Trump Jr. with something to get him to flip on his father. But so far, there's been no evidence that Trump knew about that meeting, and Trump continues to deny it.
More and more, the Democratic hope for a deus ex machina to oust Trump seems like a chimerical fancy. (Even if Trump were to be indicted for a crime, it's utterly unclear constitutionally whether he could be prosecuted; the constitutional remedy for high crimes and misdemeanors is impeachment.)
But they do have one hope yet: Trump could continue to pour out his feelings on Twitter, creating possible legal problems for himself and undermining his credibility with the American people.
That's why Trump should stop chatting about these matters. The more he chats, the higher the chances he creates a thicket he cannot escape.
The Democrats' best hope at this point isn't the law or even Robert Mueller.
It's President Trump's rage, and his pathological inability to avoid venting it in public fora.