When President Trump fired FBI Director James Comey, his stated justification for doing so — that Comey had mishandled the Hillary Clinton email investigation by essentially being too tough on Clinton — didn’t make a whole lot of sense considering, well, everything Trump has ever said about that topic.

So speculation immediately arose that the true reason for Comey’s dismissal was because Trump was unhappy with the FBI’s investigation into Trump associates, Russia, and the 2016 election.

And since the firing, more and more reporting is corroborating that theory — a theory that of course would mean the president was trying to obstruct an investigation that could implicate him or people close to him.

On Wednesday, a new report from CNN’s Jake Tapper quoted a “source close to Comey” claiming that Comey was fired for two reasons — first, because he refused to provide Trump “with any assurance of personal loyalty,” and second, because the FBI’s Russia investigation was not going away and instead “was accelerating.”

Tuesday night, Politico’s Josh Dawsey reported that, per his sources, the decision to oust Comey came from the president and not the Justice Department. For more than a week, Dawsey writes, Trump “weighed firing” Comey because, according to two advisers, “he had grown enraged by the Russia investigation” — not the Clinton email case. He continues:

[Trump] repeatedly asked aides why the Russia investigation wouldn’t disappear and demanded they speak out for him. He would sometimes scream at television clips about the probe, one adviser said... ...[A White House] spokesman said Trump did not ask for the [Justice Department] letters in advance, and that White House officials had no idea they were coming. But several other people familiar with the events said Trump had talked about the firing for more than a week, and the letters were written to give him a rationale for firing Comey.

On Wednesday, the New York Times’s Matthew Rosenberg and Matt Apuzzo reported that just days before Comey was fired, he had asked the Justice Department “for a significant increase in resources for the bureau’s investigation into Russia’s interference in the presidential election.” Their sources were four congressional officials, including Senate Minority Whip Richard Durbin (D-IL).

Later that day, the New York Times’s Maggie Haberman and Glenn Thrush filed their own report stating that, “according to people close to the president,” Trump “had been openly talking about firing Mr. Comey for at least a week.” And on Monday, the day before the firing, they add, “Trump told people around him that he wanted Mr. Comey gone, repeatedly questioning Mr. Comey’s fitness for the job and telling aides there was ‘something wrong’ with him.”

While perhaps not particularly surprising given what we know of this administration, the evidence piling up that Trump fired Comey because of the Russia investigation is deeply significant. As Matt Yglesias writes, obstruction of justice “featured heavily in the articles of impeachment that drove Richard Nixon from office.”

And though this shouldn’t really have to be stated, it’s also deeply wrong and worrying. Through this firing — and those of other top Justice Department officials earlier this year — Trump has shown that he feels no obligation to respect norms of independence for the top United States law enforcement agencies. The question is whether congressional Republicans will force him to do so.