The old saw that the cover-up is worse than the crime often obscures more than it reveals. But in the case of President Donald Trump’s firing of FBI Director James Comey, it carries an important element of truth. It escalates the administration’s Russia scandal, and, for the first time, provides indications of impeachable offenses.

Nothing we’ve seen credibly reported thus far about Trump and Russia would amount to an impeachable offense, and indeed, it’s not really clear what allegations of “collusion” on the campaign trail would really amount to even if proven.

Firing the FBI director in order to obstruct an ongoing investigation would be different.

That obstruction charge is, of course, unproven as of Wednesday afternoon. But the probable cause is everywhere. And it makes a sham of the notion that replacing Comey with a well-qualified director or continuing with existing congressional inquiries is a sufficient remedy.

There needs to be a separate investigation — featuring sworn testimony from the key players and subpoenas of documents — into why Comey was fired. Was it because Trump suddenly decided in mid-May that Comey’s handling of the Clinton emails was unforgivable, or was it because Trump was trying to obstruct justice?

The answer makes a huge difference.

Media reports suggest obstruction of justice

Anonymously sourced journalism is not the same thing as sworn testimony or hard evidence. But it’s also indispensable to uncovering official wrongdoing. And Tuesday evening and Wednesday morning already brought forth plenty of evidence of wrongdoing:

Some or all of this reporting may prove to be false. But it has all been published by credible journalists in credible publications. And it adds up to a very clear picture of a president deciding to fire an FBI director to obstruct an ongoing investigation and then stitching together a shaky rationalization for doing so.

Impeachable, if true

Impeachment is, of course, a political process rather than a judicial one. Trump will be impeached and removed from office if a critical mass of members of Congress want him to be, and not otherwise. There are no formal criteria.

But obstruction of justice featured heavily in the articles of impeachment that drove Richard Nixon from office, and also in the articles of impeachment that passed the House only to see Bill Clinton narrowly acquitted in the Senate. In short, it lies firmly in the American political tradition to regard possible obstruction of justice as a serious issue worthy of investigation in an impeachment context.

It is possible, of course, that a thorough investigation would either exonerate Trump on this score or else at least fail to produce an adequate quantity of hard evidence — documents and sworn testimony — to consider the case truly proven.

To do that, however, someone would need to take a serious look.

Journalists can do a lot, but we can’t compel testimony or force the disclosure of documents. A special prosecutor and congressional committees could. We ought to have both. But thus far, it looks more likely that we will have neither.

Republicans have their heads in the sand

The key leaders of the Republican Party are, once again, protecting and defending Donald Trump. And once again, there is a small thread of dissent, with various more vulnerable members of Congress suggesting that they find the timing suspicious or otherwise troubling. John McCain is even back to making trouble about the need for a more serious independent inquiry into Russia matters.

But while the Russia matter is, of course, important, at this point, to simply focus on Russia is to miss the elephant in the room: Trump and obstruction of justice.

Congress ought to investigate what really happened here. Did Deputy Attorney General Rod Rosenstein really write a memo about Comey’s handling of the emails that was so persuasive it convinced Sessions and Trump to both change their minds and fire Comey? Or, as seems much more plausible, was he tasked with writing up a memo that would validate an already-made decision on the theory that if the Trump administration aligned themselves with earlier Democratic criticism of Comey, they would be unable to knock him for the firing?

And if so, what was the real reason Comey was fired — and how did it relate to the president’s anger over the Russia investigation and its forward progress?

The odds that a Congress under continued GOP control will pursue such questions seem slim. During the 2016 presidential campaign, few Republicans in Congress were under the delusion that Trump’s rise to prominence was a good thing for the conservative movement. They worried, overwhelmingly, that his erratic ways were going to drag them down with him.

Ever since Election Day, they have operated in a strange moral and intellectual miasma that’s led them to forget all that and invest their energy in defending him, believing that to be the best path forward for American conservatism. One can only hope at this point that they’ll reconsider before it’s too late. If not, America is going to need a different group of Congress members.

Watch: How to impeach a president