Special counsel, Robert Mueller Saul Loeb | AFP | Getty Images

The evidence that Trump obstructed justice seems stronger than the evidence of collusion

We know for a fact that Mueller is looking into potential obstruction charges. On January 4, the New York Times's Michael Schmidt reported that Trump ordered the White House counsel, Don McGahn, to convince Attorney General Jeff Sessions not to recuse himself from the Russia investigation. When McGahn failed, "the president erupted in anger in front of numerous White House officials, saying he needed his attorney general to protect him," Schmidt writes. "Mr. Trump said he had expected his top law enforcement official to safeguard him." The incident suggests that the president wanted law enforcement officials to protect him from criminal charges. And indeed, Schmidt reports that the episode was initially discovered by Mueller "as he investigates whether Mr. Trump obstructed the F.B.I.'s Russia inquiry." The irony, according to many experts, is that this kind of effort to block the Russia investigation has likely created a bigger legal problem for Trump than anything he may have done with Russians. "So-called 'offenses against the administration of justice' — like obstruction of justice or lying to the FBI — are often easier to prove than the underlying criminality that the subject was trying to hide," says Jens David Ohlin, a professor of law at Cornell. "In Trump's case, this is undoubtedly true." There's clear evidence that some of Trump's campaign staff were in contact with Russian officials, and even interested in receiving their help in the election. The best example is the June 2016 Trump Tower meeting, where Donald Trump Jr. met with a Kremlin-linked attorney who was promising to provide dirt from the Russian government on Hillary Clinton. But to link Trump himself to collusion, you'd need to prove that he had personally approved of this meeting, or that the Trump campaign as a whole was involved in a broader plot to work with the Russian government. In the absence of this evidence, experts say it would be very hard to charge the president with any kind of collusion-related crime. And no such evidence exists, at least in the public record. "Nothing, to my knowledge, has come out that implicated [Trump] directly," says Asha Rangappa, a former FBI special agent and current associate dean of Yale University. The public evidence that Trump committed obstruction of justice — defined as "corruptly" attempting to "influence, obstruct, or impede, the due administration of justice" — is quite a bit stronger, particularly when it comes to the Comey firing. Technically, the FBI director serves at the pleasure of the president and can be fired at any time and for any reason. However, the general belief among experts is that it's not legal for the president to use this power in an attempt to shield himself or his family members from criminal investigation. Crucially, it does not matter whether Trump successfully shielded himself from scrutiny — all that matters is that he tried to. "The obstruction statutes are very broad," Griffin explains. "It matters whether Trump 'endeavors' to impede the DOJ and congressional investigations at any turn." This all hinges on what was in the president's mind when he fired Comey. If Trump did it because he thought Comey was doing a poor job supervising the Russia investigation, that's perfectly legal. If he did it because he was worried that Comey's investigation might end up uncovering some kind of misdeeds by the Trump family — whether Russia-related, financial, or otherwise — then that's obstruction. Typically, proving intent is difficult for prosecutors, because establishing what a person was thinking at a particular moment is inherently challenging. But Trump has made things easier for Mueller — by repeatedly, even publicly, admitting that he fired Comey out of hostility to the Russia investigation. There's an interview with NBC's Lester Holt in which Trump admits to removing the FBI chief because he felt "this Russia thing with Trump and Russia is a made-up story." There was Trump's meeting with Russian Foreign Minister Sergei Lavrov the day after the firing, where he told the foreign diplomat that "I faced great pressure because of Russia [and now] that's taken off." And then there are his endless tweets about how he thinks the Russia investigation is a "witch hunt" and should be shut down. "He's kind of making the case himself for Mueller [on] obstruction," Rangappa concludes. Firing Comey isn't the only possible Trump action that could land him in hot water on obstruction charges. But the firing is the clearest example based on what we know right now — and one that seems more likely to form the backbone of any charges against Trump than anything directly related to Russian collusion.

We are still a very long way away from indictment or impeachment