President Donald Trump speaks in the East Room at the White House in Washington, Monday, June 5, 2017. Trump is making the case for privatizing the nation's air traffic control system. (AP Photo/Carolyn Kaster)

Thursday’s testimony by fired FBI Director James Comey was the capper on months-long revelations that President Donald Trump is an egregious serial liar who no longer commands the credibility needed to be president.

Trump has given himself no choice now but to resign or face inevitable impeachment.

Unrepentant, Trump immediately doubled down on his lies today after Comey’s shocking and compelling testimony before the Senate committee charged with determining the extent of Russian involvement in the 2016 election and possible collusion with the Trump Campaign.

Comey’s testimony was laudable and believable. Trump’s broken connection with the truth, reality and any normal sense of scruples simply resulted in just more of Trump after the hearing.

For now, the choice is still Trump’s. But the entire country, and the entire world, knows full well that nothing he nor his top aides say is believable.  At this point, Trump can rule the country, but he cannot lead it. Sadly, not only is that distinction likely lost on Trump, his self-documented behavior makes clear he prefers it this way.

Comey revealed that not only did Trump repeatedly try to steer and obstruct the FBI investigation into Russian election meddling and disgraced NSA Director Michael Flynn’s connections to the Russian government, he insisted on personal “loyalty.”

Dismissed by misguided Trump supporters, that’s a big deal. Only despots demand personal rather than patriotic allegiance. The revelation is chilling.

While Republican House Speaker Paul Ryan has excused Trump’s unethical and illegal behavior as naiveté, being a presidential novice does not excuse the presumptuous malevolence Trump’s self-documented behavior underscores. And it doesn’t address the lying.

Comey Thursday divulged that when Trump told him that he “hoped” that the FBI would “go easy” on Flynn, that he was being pressured to comply. Only partisan hacks say otherwise, as even a fool understands the innuendo of this kind of threat.

The most compelling evidence of obstruction didn’t come directly from Comey’s testimony, however, it came from Trump himself, who freely admitted weeks ago that he fired the FBI direction because of his role in the Russian investigation. Trump has made clear he wanted the investigation dropped, and he believed firing Comey might have that result. Surreally, Trump boasted about it to, of all people, Russian officials he invited to the White House.

Trump believed he could get away with it. Like so many things, he was wrong about that, too.

His long and well-documented trail of lies caught up with him in Thursday’s Senate hearing. Because anything and everything he says is unbelievable, he has destroyed his presidency.

The country faces a long list of grave and difficult challenges. Republicans have been empowered to implement new ideas and directions, but with Trump at the helm of his sinking ship, all Republicans and their strategies are at risk.

Almost certainly, Republicans will be unable to persuade Trump to resign, and an inevitable impeachment trial will fast become election fodder next year. The nation has too many problems to just watch Trump’s presidency burn to the ground. Sinking in an unescapable quagmire of lies, Trump must resign.