Donald Trump's impeachment trial is all but over, with his acquittal virtually certain. But its effect on the 2020 presidential election remains unclear. Trump was impeached, after all, because he withheld hundreds of millions of dollars in military aid to Ukraine in an effort to force that nation into opening an investigation into Joe Biden, based on the discredited conspiracy theory that the former vice president got a Ukrainian prosecutor named Viktor Shokin fired to cover up supposed illegal activities by his son Hunter Biden. (Trump also wanted an investigation into an even more delusional conspiracy theory, the one which holds that a Democratic National Committee server somehow wound up in Ukraine.)
Trump and his allies have made clear that they won't let this matter drop if Biden is Trump's Democratic opponent in the general election. This whole tangled affair is not easy to follow, even for political insiders, and has at least two intersecting vectors: First, what did Trump do in Ukraine and Russia, and what are the ramifications for foreign policy and the global order? Second, how will Biden's campaign react to Trump's false or exaggerated accusations, especially given the long GOP history of throwing mud at Democratic presidential candidates?