Every crisis has a tipping point. Ever since he took office as President, Donald Trump has been under threat of impeachment. He has cut such a malign and ludicrous figure as the Leader of the Free World that it seemed only a matter of time before he finally went too far even for what has proved to be a morally derelict, Republican Party.

But the moment never came. Trump survived every scandal, every excess, every racist tweet. It was as if nothing could stop him and the only question was, could he go on to win a second term?

Until now.

Now he has done it. The truth is out there in all its gory detail. Whether or not Trump will still be in the White House a month from now is the question on everybody’s lips.

On Tuesday, members of the US House of Representatives investigating Trump’s dealings with the Government of Ukraine – the diplomatic equivalent of the dark web – took a dramatic turn when the outgoing U.S. ambassador to Kiev, Bill Taylor, gave evidence that demonstrated beyond all doubt that Trump had made military aid to Ukraine conditional on its government dishing dirt on former Vice President Joe Biden, currently the front runner to be his democratic opponent in the 2020 presidential race.

This was dynamite. Until Taylor took the stand, Trump and his team, including Secretary of State Mike Pompeo, looked as if they might get away with their claim that no “quid pro quo” had been sought in return for the military equipment and that a seemingly damning telephone conversation between the two leaders released after revelations of its content by a CIA whistleblower had in fact been misconstrued as part of an ongoing Democratic witch hunt.

“No quid pro quo” became the Administration’s mantra, issued by every Republican and every White House spokesperson whether in Congress or on television or when answering questions from the press.