Crises make and break historical reputations. In our current constitutional emergency, a few unlikely figures, above all the former Attorney General Jeff Sessions, have upheld the rule of law, possibly redeeming their places in history. Many others, above all the current Attorney General, William Barr, seem determined to irretrievably sink theirs. Now the reputation at risk is that of the House Speaker, Nancy Pelosi.

With regard to the debate over the proper response to Donald Trump’s brazen deeds, Pelosi has not taken impeachment off the table, saying, “I don’t think you should impeach for political reasons, and I don’t think you should not impeach for political reasons.” Yet political reasons seem to be preventing her from pursuing constitutional concerns. Her reasoning is clear: if the House were to launch an impeachment without “overwhelming” evidence of high crimes and misdemeanors and strong bipartisan public support, Trump’s inevitable acquittal in the Republican-controlled Senate would only strengthen him, and he could cruise to reëlection. But, in this instance, Pelosi’s normally acute political judgment is failing her, and the historical precedent she is evidently relying on—the impeachment of President Bill Clinton—is not analogous. In fact, based on the past half century of political history, suppressing an impeachment inquiry seems more likely to help insure Trump’s reëlection. If this happens, Pelosi’s formidable reputation, based on a lifetime of public service and her role as the first female Speaker of the House, will suffer.

The basic historical error behind suppressing an impeachment inquiry confuses the genuine crisis surrounding Trump with the manufactured one that engulfed Clinton. In 1998, the House Republicans, lacking public support and all but assured that the Senate, though it was controlled by their own party, would not convict Clinton, impeached him anyway, which only served to win him sympathy and drive up his popularity ratings. Pelosi apparently sees the same thing happening now, but the two cases are very different.

When the scandal involving Clinton and Monica Lewinsky broke, in January of 1998, Republicans had been pursuing both Bill and Hillary Clinton for more than five years, and they had come up with nothing. In the view of most Americans, the Lewinsky story, although pathetic and unnerving, never amounted to a case sufficient to justify Clinton’s removal from office, even when attached to Clinton’s dissembling under oath about the matter. Moreover, Clinton, unlike Trump, was a broadly popular President: when the scandal broke, his approval rating hovered around sixty-six per cent; on the day he was impeached, it rose to seventy-three per cent; the week after his acquittal, it was the same as it had been at the beginning: sixty-six per cent.

Trump, by contrast, is the least popular President of the postwar period, who enjoys a fiercely loyal base but so far has failed to win the support of more than half those Americans polled. More important, the evidence presented in the Mueller report—regarding the Trump campaign’s expectation that it could benefit from Russian interference and hacking efforts, and numerous contacts with Russians, as well as the President’s subsequent attempts to obstruct justice—is formidable, if, in Mueller’s view, insufficient to “establish” that members of the Trump campaign actually conspired or coördinated with Russia. (The insufficiency, of course, may have been due to the efforts at obstruction that the report describes.) Despite Barr’s efforts to obscure the fact that Mueller’s report does not exonerate the President, only thirty-three per cent of Americans, according to a Quinnipiac poll, believe that the Attorney General has accurately represented the report’s conclusions. That number may fall further after Mueller’s testimony before Congress, which is scheduled for next week.

The more relevant historical analogy to Trump’s situation is that of President Richard M. Nixon, during the last two years of his Administration. Nixon won reëlection in a historic landslide in 1972, but his public standing eroded during the summer of 1973, when the televised Senate hearings chaired by Senator Sam Ervin, Democrat of North Carolina, began to reveal the extent and the seriousness of the Watergate crimes. Even so, at the start of 1974, less than thirty-eight per cent of the public were in favor of removing the President from office, and support for Nixon among Capitol Hill Republicans remained strong. A major reason for Nixon’s continued support was the effectiveness of his Administration’s stonewalling strategy of denial and redaction—the same strategy that the Trump Administration has pursued in fighting subpoenas from several current House committees. (On Thursday, the Judiciary Committee voted to issue subpoenas to a dozen people associated with the White House, including Sessions and Jared Kushner.) Still, support for Trump’s impeachment stands at forty-five per cent, according to a June Gallup Poll.

In 1974, the Democrats did not flinch. Based on what was known after the Ervin Committee inquiries—which was nowhere near as conclusive as the evidence amassed against Trump by Robert Mueller—the House Judiciary Committee authorized its chairman, Representative Peter Rodino, of New Jersey, to undertake an impeachment inquiry. That inquiry, alongside the continuing work of the special prosecutor Leon Jaworski, produced the evidence and sustained hearings that decisively turned public opinion—and led to Nixon’s resignation.

In short: Nixon, a popular President who retained public support, finally succumbed to powerful charges once the House fulfilled its constitutional duty. Yet now an unpopular President may get away with acts at least as grievous as Nixon’s because the House will have evaded its constitutional duty. The blame for that evasion would fall on Nancy Pelosi.

Pelosi, more surprisingly, is also ignoring the chief political lesson of the Nixon impeachment. The case against authorizing an impeachment inquiry rests in part on polling, which shows that the public over all remains unconvinced that an impeachment inquiry is warranted—though the number in favor keeps growing. Yet had the House Democratic leadership come to the same conclusion in early 1974—when, it needs remembering, public support for impeachment was actually weaker—Nixon would have finished out his second term. The lesson is simple: on matters as serious as a Presidential impeachment, the opposition must lead, not follow, public opinion; it must examine and develop the evidence in plain view, and not permit the White House to persist in shaping perceptions through concealment and lies.

Another lesson follows from this one. Asserting that a Senate acquittal would allow Trump to claim vindication elides the fact Trump has already claimed vindication, a falsehood which the Democrats’ failure to pursue impeachment would only strengthen. It also overlooks how a Senate trial always reinforces either the severity of the alleged crimes and the persuasiveness of the evidence, or the lack thereof. Nixon resigned only when Senate Republicans told him that his case would not survive a trial. Trump’s domination of the G.O.P. does make it all but impossible that the Senate would vote to remove him. But evidence presented by the House impeachment managers would enrage independents as well as Democrats, on the eve of the election, putting pressure on vulnerable Senate Republicans as well as on Trump. The electorate would, in effect, do the job that the Senate refused to do.

Pelosi, viewing the House and Senate proceedings narrowly, argues that Trump is best contested not with impeachment, which would be divisive, but by replaying the kitchen-table issues that won the Democrats the House majority in 2018—health care, immigration, and climate change. But that strategy would commit the classic military blunder of fighting a war on the basis of the last successful campaign, regardless of the facts and context. It’s one thing to defeat Republicans in congressional races in which Trump’s name does not appear on the ballot. It’s quite another to defeat them when the charismatic Trump heads the ticket and is able to claim that he is exonerated because Democrats did not pursue an impeachment inquiry. In any event, the campaign so far has showcased that Democrats are far from united on a number of kitchen-table issues, from Medicare for All to the Green New Deal.