It’s likely that many Democrats privately share that belief, and new developments this summer and fall—Paul Manafort’s current fraud trial, fresh leaks from Michael Cohen, another round of indictments, the long-awaited release of Robert Mueller’s report—may well cement the belief among Democrats that a newly captured Congress should pursue impeachment if the weight of the evidence warrants it. In fact, there’s already an impeachment constituency; in a CNN/SSRS poll from last month, 42 percent of Americans said Trump should be impeached and removed—virtually identical to the 43 percent who said that about Richard Nixon, in a Harris poll, five months before he resigned in 1974.

But Democratic leaders—Nancy Pelosi, Chuck Schumer, the people running the House and Senate campaign committees—utter the I word only when asked, and only to insist that whatever Democrats may believe about Trump’s culpability, campaigning about it would be bad politics. When Rolling Stone recently broached the topic while interviewing Pelosi, she said that the issue would be “a gift to the Republicans … I don’t think it’s in the interest of America’s working families to focus on that, unless we have more [evidence] to go on, which we don’t at this time … What we’re [emphasizing] is the economic security of working families.”

She’s arguing that Democratic candidates need to reconnect with voters (who deserted the Democrats in the red-wave midterms of 2010 and 2014) by prioritizing kitchen-table issues that affect their daily lives—most notably health care, which polls very well for the party at the GOP’s expense. A new national poll, released Tuesday, shows solid support for protecting or expanding Obamacare (including 63 percent of “never Hillary” independents) and solid disapproval for Trump’s health-care policies (including 64 percent of those independents). Pelosi doesn’t want to “gift” the Republicans a constitutional crisis issue that could infuriate—and further energize—Trump’s GOP base, which is already stoked by the “witch hunt” trope.

Norman Ornstein, a resident scholar at the American Enterprise Institute and a fervent Trump critic, told me that Democrats are smart to leave the I word alone. He happens to believe that Trump in Helsinki “met the constitutional test for treason, the most clear-cut high crime and misdemeanor.” But talking about that on the stump would likely collide with the political facts of life. Ornstein, who has analyzed Congress and national politics since the ’70s, said:

I can understand the caution that many Democratic leaders feel … It’s the fear that talk of impeachment will motivate tribal Republicans. The normal pattern in a wave election is that the president’s party is demoralized, disillusioned, and depressed, and doesn’t turn out, while the [out of power party] is upset and angry, and does. But remember, we’re now driven by negative partisanship—people motivated more by the desire to keep the evil forces on the other side from destroying our way of life than they are motivated by attachment to their own. So a widespread call for impeachment could ignite a strong reaction from Trump voters to show up and defeat the enemy, even if they’re not so happy with Trump’s bombast, corruption, sellout to Putin, and trade war.

Veteran Democrats also remember what happened in 1998 when Republicans stumped in the midterms for the impeachment of President Bill Clinton. House Speaker Newt Gingrich led the chorus, and the GOP expected big gains on Election Day. The strategy flopped. Republicans lost three House seats, and Gingrich promptly quit. The lesson of the episode: Impeachment, as a partisan issue, is a loser on the trail.