The surest sign that a sitting president has problems is when members of his own party start to turn on him.

And that appears to be happening with Donald Trump. First, Tennessee’s own Bob Corker said Monday that the Trump White House is in a “downward spiral,” following reports that Trump shared classified information on the Islamic State with Russia.

Two days later, Congressman Justin Amash, a Michigan Republican, said it would be an impeachable offense if Trump fired FBI director James Comey to end an investigation. His comments followed a report in the New York Times on Tuesday that alleged Trump had pressured Comey to stop an investigation of disgraced former national security advisor Michael Flynn.

It should go without saying that neither Corker nor Amash are part of the far-right coalition of the Republican Party. Corker is a Baker Republican, a moderate. And Amash was one of just two Republicans to side with Democrats in their request of an independent investigation into Trump’s ties with Russia.

Nonetheless, Trump has a major problem, and it’s only getting worse. His administration cannot continually dismiss bombshell revelation after bombshell revelation as “fake news.” The Washington Post’s story on the sharing of classified information and the New York Times revelation on the Flynn memo are potential game-changers, particularly the latter. Even stalwart conservatives who defend Trump’s decision to share the Israel intelligence will have a difficult time excusing the firing of the director of the nation’s top law enforcement agency because the agency dared to investigate a member of the president’s panel…if that is indeed what happened.

Republicans aren’t going to mount a serious investigation of Trump, and they’re certainly not going to undertake impeachment proceedings. The Nixon era is long behind us, and in these hopelessly partisan times, there is no Howard Baker to ask what the president knew and when he knew it.

But if Democrats win back control of Congress in next year’s midterms, Trump’s problems are going to get a lot worse in a big hurry — because no holds will be barred. Whether they’re successful in ousting the president, which will always be a very long shot in this modern era of politics, the backlash will almost certainly place a Democrat in the White House in 2020.

Not everything about the Trump presidency has been bad. But the remarks of Corker, who hails from a deeply red state that voted overwhelmingly for Trump, are a sign of the times. This administration is in a downward spiral. If its course is to be reversed, Trump will likely have to check his ego. So far, that’s proven difficult for him to do.