One of our perennial school pranks was to place a whoopee cushion secretly on the chair of an unsuspecting teacher. When she sat, she would launch the resounding clap of flatulence. That, metaphorically, is what just happened to Speaker Nancy Pelosi. Unfortunately, she placed it on her own chair. The embarrassing noise sounded when she announced she would delay sending the House’s Articles of Impeachment to the Senate.This delay was a nakedly partisan ploy — and a major error of political judgment. Every day it continues will cost Democrats in the general election.Why?First, the Democrats should be emphasizing only the constitutional necessity of impeachment. That’s why Speaker Pelosi wore funereal black for the House vote, why she tried in vain to stop jubilant Democrats from taking selfies after the vote. (She seemingly couldn’t control Washington Post reporters, who did the same thing. Democracy dies in derangement.) The delay highlights the Democrats’ raw political calculations. Of course, those calculations are always the drivers for both parties in Washington. What Pelosi’s stunt does, though, is put them front and center.The real motives are painfully obvious. Democrats want Trump out not for some specific reasons (the articles of impeachment are virtually inkblots) but because they truly, deeply hate him. Republicans want to keep him, most because they like him, some because they think the party will implode if they remove him now. Both parties are united. Impeachment only solidified their stances. Since partisan reasons for impeachments are widely condemned as illegitimate, proponents must build bipartisan support and show their rationale rises above party. In Nixon’s case they did; in Bill Clinton’s case, they failed. They failed again in Trump’s case. The hearings chaired by Adam Schiff and Jerry Nadler did nothing to weaken Republican support for Trump and actually undermined it slightly among independents. Pelosi is now compounding the damage.Refusing to hand impeachment articles to the Senate looks like partisan pique because it is. Does anyone really think the goal is to ensure fairness? The Speaker’s claim would be credible only if House procedures had themselves been scrupulously fair, if they had allowed Republicans to call witnesses, if they had promptly shared witness transcripts, if they had allowed the president’s lawyers to participate in his defense. They didn’t.Earlier impeachments had been even-handed. This one wasn’t. Because House Democrats ran their impeachment Frank-Sinatra style — ‘I did it my way’ — their call for different procedures in the Senate rings hollow. The only question now is whether independent voters will buy what Pelosi is selling. That’s doubtful, and Republicans will pounce on it.Second, the delay undercuts a central Democratic rationale for impeachment, that Trump’s remaining in office is a clear and present danger. That was the main reason Democrats gave for rushing through the hearings and votes, for refusing to wait for federal courts to decide on White House claims of Executive Privilege. That argument bleeds out, fatally, every day Pelosi delays.Finally, delay brings us closer and closer to the November 2020 vote, when citizens can decide for themselves. Impeachment and removal are designed to prevent that choice. Again, that rationale is most compelling if the danger is both grave and immediate. Choosing to delay destroys that argument. It says, unmistakably, we can afford to wait.Why do it, then? Perhaps it is simple misjudgment, either of the public response or the Senate’s, which is sure to defend its prerogatives. More likely, it is Pelosi’s calculation that she cannot maintain her speakership if she opposes the left-wing of her caucus. She made the same calculation when she finally agreed to impeachment hearings. She must think it is better to risk a possible Democratic loss of the House next November than to risk losing her leadership when that election is over. On that, she may well be right. She certainly knows better than outsiders how to judge her caucus’s votes and her party’s activist sentiments.Still, it is a dangerous game, one the public is far more likely to see as cynical, partisan manipulation than as sober, constitutional responsibility. For the country’s sake, Speaker Pelosi should remove the whoopee cushion now, before she sits on it again.Charles Lipson is the Peter B. Ritzma Professor of Political Science Emeritus at the University of Chicago, where he founded the Program on International Politics, Economics, and Security.