Donald Trump has a problem with elections. Seemingly lacking confidence in his ability to win them through honest and untreasonable means, he has repeatedly questioned the integrity of the American electoral system while seeking the help of foreign powers to tip the balance in his favor. From suggesting he might not accept the results of an election based on the lie that “millions of illegals” are able to cast votes to openly welcoming the help of Russia in 2016, Trump has made it clear that he cannot be trusted to oversee the presidential election of 2020.

Sadly, in the months following the fizzle which marked the end of the Mueller investigation, this basic truth has slipped out of focus. A coalition of Republicans for whom Trump can do no wrong, Democratic lawmakers worried about the politics of impeachment and progressive commentators who claim that holding Trump accountable for his conduct is a distraction from the pocketbook issues which most concern voters has come together to urge the nation to move on.

Donald Trump, meanwhile, has not moved on. We now know that just a day after Mueller’s testimony to Congress in July, Trump was once again attempting to work with a foreign power to influence a US election.

In a phone call on 25 July, Trump pressured the Ukrainian president, Volodymyr Zelenskiy, to come up with dirt on the business activities in Ukraine of Hunter Biden, the son of the leading candidate for the Democratic nomination, Joe Biden. Shortly beforehand, Trump had suspended $400m in US military aid for Ukraine, presenting the new Ukrainian president with an apparent choice: come up with some incriminating information on Hunter, or lose aid desperately needed to defend against the Russian invasion of eastern Ukraine.

If these facts – which are based on reporting and the apparent contents of a whistleblower complaint filed against the administration – are correct, they are a clear example of the kind of “high crime and misdemeanor” for which impeachment is the intended remedy. Even if Trump did not explicitly offer Zelenskiy a quid pro quo, his attempt to enlist Ukrainian help against his chief political rival is a blatant perversion of Trump’s constitutional duty to uphold the common good rather than using the powers of office to seek his own narrow self-interest. Indeed, curbing the influence of foreign countries over American politics was one of the chief concerns of the founders when they wrote the constitution.

Beyond the specific facts of this scandal, there is a broader truth which now points inescapably towards impeachment: Donald Trump is not a man who can be trusted to oversee the continued functioning of American democracy.

If the Ukraine scandal is allowed to melt into the ether in much the way the Russian scandal has done, there is no telling where Trump might stop in his attempts to tip the scales in 2020

Opponents of impeaching the president often point out that voters will have a chance to toss Trump out of office in 2020, and it is better to wait for this remedy rather than reaching straight for impeachment. But this is a weak argument indeed when Trump’s actions target the very ability of voters to exercise their rights in free and fair elections. Congress would not be pre-empting the voice of voters but defending their ability to be heard in the first place.

Congress must also be mindful of precedent. If the Ukraine scandal is allowed to melt into the ether in much the way the Russian scandal has done, there is no telling where Trump might stop in his attempts to tip the scales in 2020. And there is even less telling how far a future president – perhaps one more rational and competent than Trump – might go in undermining American democracy if the precedent is established that there is no penalty for doing so.

No one should be so naive as to believe that an impeachment push by Democrats in the House of Representatives, where Democrats hold a majority, is likely to end in Trump’s conviction by the US Senate, where they are a minority. Republican senators are not likely to convict Trump absent some large shift in conservative grassroots opinion, and the rightwing media echo chamber makes such a shift almost inconceivable. But it is just as inconceivable that Democrats should be expected to simply go along with Republican members of Congress as they shirk their own constitutional duty to oversee the conduct of the president.

But nor will impeachment necessarily be good for the president and bad for Democrats, as many commentators seem to assume. Perhaps some voters will think Democrats are wasting their time investigating Trump’s attempts to undermine American democracy, but this view seems to give voters little credit. It is clear from his approval ratings, which are abysmally low despite a strong economy, that Trump suffers from the fog of corruption and malfeasance which surrounds his administration. Impeachment investigations will make clear quite how thick this fog is, and provide a ready framework in which to fit each new outrage that Trump will inevitably commit between now and November 2020.

Politics aside, the broader truth is that American democracy is in such peril that a defense of its principles is now much more important than any short-term political calculation. Donald Trump has made it clear that these principles mean nothing to him, and the constitutional remedy is clear. Responsible members of Congress must act. If not now, as the very integrity of American democracy is threatened by an executive which considers itself not bound by law, then when?