The president doesn’t deny this. “The conversation I had was largely congratulatory,” Trump said on Sunday. “It was largely corruption — all the corruption taking place, it was largely the fact that we don’t want our people, like Vice President Biden and his son,” contributing to “the corruption already in the Ukraine.” The president confessed this again on Monday, while speaking at the United Nations. “We’re supporting a country. We want to make sure that country is honest,” Trump said. “If you don’t talk about corruption, why would you give money to a country that you think is corrupt?”

There’s no mystery here. Trump doesn’t care about corruption — he runs a network of clubs and hotels where interested parties can spend huge sums and curry favor with the administration — but he is worried about Biden’s popularity with Democrats and the wider public. The former vice president leads in nearly every head-to-head matchup with Trump. If the election were held today and Biden were the nominee, Trump would likely lose by double digits.

But if Trump can make 2020 another race between two unpopular nominees — if he can sully his opponent and make him another creature of “the swamp” — then he has a shot at victory. Imagine a world where the Ukrainian government enters the election on behalf of Trump. The president can now do to Biden what he did to Hillary Clinton in 2016 — mire him in enough scandal and innuendo to undermine the vice president’s claim to honesty. “Crooked Hillary” seamlessly becomes “Crooked Joe.” And Biden is vulnerable. He has spent his entire adult life working in Washington, and there’s little question that his son is involved in the kinds of buck-raking and influence peddling that alienates voters and makes them cynical about politics.

As for the other parts of Trump’s unusual 2016 victory, there isn’t — as far as we know — an F.B.I. investigation of Biden or any other Democratic candidate. But Attorney General William Barr has already shown his willingness to use the law in Trump’s favor, and Trump brought him up in his call with Zelensky. It was Barr, of course, whose misleading summary of the Mueller report initially defused criticism and stymied efforts to hold the president accountable for his attempts to obstruct justice.

Given this commitment to the president’s political interests, it’s not hard to imagine how Barr might use “revelations” from the Ukrainian government to pursue an inquiry into the former vice president and his son, releasing information at a pace that feeds the story, strengthens the appearance of impropriety and ultimately undermines Biden’s campaign. Trump, at least, thinks the attorney general is up to the task. In Trump’s conversation with President Volodymyr Zelensky of Ukraine, Trump referred him to Barr . “There is a lot of talk about Biden’s son, that Biden stopped the prosecution, and a lot of people want to find out about that,” the president said to Zelensky, according to a recently released reconstructed transcript. “So whatever you can do with the attorney general would be great.” The attorney general of the United States, that is.