Americans continued to approve of Clinton’s job performance, polls showed, but many also said they disapproved of him personally. The discomfort helped define the 2000 presidential race, in the views of both Gore’s campaign and George W. Bush’s.

Bush made it his mantra to “restore honor and dignity” to the White House. Gore chose Joe Lieberman, arguably Clinton’s highest-profile Democratic critic, as a running mate. “Everybody who said the economy was so good, you should just run on Clinton’s record — they weren’t sitting in focus groups in swing states, listening to these swing voters who were concerned there would be a continuation” of unethical behavior, Tad Devine, a Gore adviser, recently said to The Atlantic’s Ron Brownstein.

Shortly after the election, Thomas E. Mann of the Brookings Institution wrote: “Most Americans were appalled by his behavior; he never regained the personal standing he enjoyed before the scandal.” Had Clinton campaigned heavily in the 2000 race, Mann added, “The evidence was overwhelming that he would have done more harm than good with swing voters in battleground states.”

True, Gore was a flawed candidate, and a stronger one may well have overcome the scandal. But it did make his job harder. He lost a large share of voters who approved of Clinton’s performance but disapproved of Clinton personally, as the Democratic pollster Stan Greenberg told me. And loyal Republican voters, frustrated by Clinton’s acquittal, turned out in big numbers, Matthew Dowd, a top Bush adviser, has said. In the end, Gore won the popular vote only narrowly, despite the strongest economy in decades, and lost the election.

Over the next eight years, Republicans continued to hold the White House and usually controlled Congress. Only Bush’s unpopular presidency — Hurricane Katrina, the Iraq War, the financial crisis — delivered control back to the Democrats. It’s impossible to know how things would have played out if Republicans had skipped impeaching Clinton, of course, but there is little sign they paid much of a price, if any, for doing so.

Today, every argument for impeachment is stronger than in 1998. On the politics, a greater share of Americans already support impeachment than ever did in 1998, while Trump’s approval rating is a meager 42 percent. On the substance, I think that Clinton’s behavior was in a gray area of “high crimes and misdemeanors”: odious, illegal but largely personal. Trump’s behavior is spectacularly impeachable, involving one of the founders’ central justifications: foreign interference.

Trump deserves to be impeached on the merits, and, if he is, it will probably further sully him in the eyes of swing voters, much as it did to Clinton. The big question now is how well will Democrats handle the process. They should move quickly to hold more public hearings, rather than the private sessions they held last week, so Americans can better understand how Trump has perverted American foreign policy and national security for his own benefit.