Republicans push the bar ever lower. This president still cannot clear it. Even a month ago, Democrats were at pains to stress that a request for foreign interference in domestic politics was impeachable in and of itself, whether or not Donald Trump had offered a quid pro quo to the Ukrainian president, Volodymyr Zelenskiy. There was a principled reason for this. Mr Trump and his supporters should not be allowed to present the manipulation of US diplomacy for private interests as normal practice. A country like Ukraine is hardly in a position to antagonise the American president; no explicit threat or inducement need be added to the scales. But in any case, the bargaining simply makes a terrible act much worse.

Of course, the Democrats had a pragmatic reason for drawing the line: the knowledge that it might be hard to prove the attempted trading of interests. This is why Tuesday’s testimony to impeachment inquiry hearings by Bill Taylor, the acting ambassador to Kyiv, drew gasps. It is not a surprise to anyone that the president should pursue such a course. But Mr Taylor, a veteran diplomat, laid out clearly, precisely and damningly how Mr Trump sought to make a summit meeting and military aid to Ukraine conditional on its government launching two investigations: one into his political rival Joe Biden and his son Hunter, and another into the conspiracy theory that it was Ukraine (not Russia) that interfered in the 2016 election to benefit Hillary Clinton (rather than Mr Trump).

The ambassador’s evidence, building on testimony from the former top Russia adviser Fiona Hill, and his ousted predecessor Marie Yovanovitch, laid out the way this administration created a foreign policy back channel for this purpose, undermining its conventional diplomacy. It was run by the president through his personal lawyer Rudy Giuliani and figures including the ambassador to the European Union, Gordon Sondland, a donor to Trump’s inauguration with no former diplomatic experience.

Mr Taylor says Mr Sondland told him there was no quid pro quo – before spelling out an arrangement that is the very definition of a quid pro quo. Last week the acting chief of staff Mick Mulvaney agreed that there was, but that it only related to 2016 – so “get over it”. (He subsequently walked back his remarks.) The White House continues to insist that there was no quid pro quo. To claim that no quid pro quo existed is like the rest of us claiming that Mr Trump is not the president. Life would be better if it were true, but wishful thinking does not make inconvenient facts disappear.

The past cannot be undone, and things can be improved only if there is the will to do so. The Democrats’ will was galvanised when they launched impeachment proceedings. Republicans are still floundering. Most managed to criticise Mr Trump’s claim that he was facing a “lynching”, a deliberately offensive and ridiculous attempt to distract from Mr Taylor’s evidence and to rally his base with racialised imagery. But they continue to balk at taking him on for fear that they will be politically punished. Mitch McConnell, the Senate majority leader, refused to back Mr Trump’s claims that he had described the president’s call with Mr Zelenskiy as “innocent”.

That is as far as he has gone. Like his colleagues, he seeks to avoid the taint of Mr Trump without actually cutting him loose. They have no will to protect the standards of office – just the hope that all this will go away if they keep lowering very basic expectations for the highest office in the land.