As I’ve said before, I believe that when a president commits impeachable offenses on a regular basis, there is a Constitutional duty to call him to account that Congress may not shirk. I think this is clearly the case with Donald Trump. To consider only the events of the past week: Trump announced that he would proceed with an arms deal for Saudi Arabia in defiance of Congress. He continued to reject any testimony to Congress by members of his administration, past or present, even under subpoena. His Justice Department issued a 17-count indictment against WikiLeaks founder Julian Assange that, as The New York Times noted, strikes a fundamental blow at a free press. He has directed the Justice Department to investigate the FBI’s legally authorized investigation of his campaign’s involvement in Russia’s meddling in the 2016 election campaign, and to declassify any and all CIA records in doing so regardless of jeopardy to ongoing operations or personnel in the field. He has accused former FBI Director James Comey and his Deputy Director, Andrew McCabe, of high treason. Need I add that presidents cannot legally accuse any American citizen of an offense, let alone treason? And that’s just the week that was.

Many commentators, and some in Congress, have given up the pretense that Trump is violating established “norms” of presidential conduct. They have called him out as a would-be tyrant who, if unchecked, will soon be an actual one. At this point, is there serious question that this is the case? Or that the framers of the Constitution vested Congress with the powers of impeachment to deal precisely with the likes of a Donald Trump — presuming they could have imagined anyone like him this side of Nero or Caligula? So, what are we waiting for? The answer, at least for Nancy Pelosi, is twofold. Pelosi is waiting for two things. One is Republicans in Congress, or at least enough of them to assure bipartisan support for impeachment. The other is Republicans in the country, some 90 percent of whom, together with some right-leaning Independents, still support Trump. The former group will not act until the latter one shifts ground. This is a political fact, and, deplore it as you will, it is like most facts — a very stubborn thing.

So, Pelosi could probably muster a party-line vote for impeachment in the House of Representatives. But the bill would fail in the Senate, and Trump would still be President. There is still a strong case to be made even for an impeachment certain to be voted down in the Senate. The hearings themselves would bring forward damning evidence, compiling a record that would remain for history and vindicate Congress’ own responsibility in an hour of crisis. It might even sway Republican opinion. Yet a failed impeachment would still be a failure. It would more likely rally than alienate Republican voters. It would fit into Trump’s central narrative, that his presidency has been beset from the beginning by “treasonous” attempts to destroy it. It is, Pelosi has concluded, exactly the mistake Trump hopes to taunt, bully and bluff the Democrats into making.And that, in her view, is the best reason to avoid committing it.

Trump’s power, Pelosi has concluded, is in his personalistic appeal to those who support him as the voice of their own disaffection from the party system. It is the appeal of a demagogue, and the costume that best suits him is that of his followers’ beleaguered champion. She’d rather see him stripped naked, exposed as he truly is. To do this, Pelosi has adopted a two-pronged strategy. The first part is to maintain a drumbeat of Congressional investigations short of an impeachment proceeding, relying at the same time on the courts to compel the disclosure of Trump’s financial records, to force compliance with subpoenas and to rein in at least some of his more egregious violations of law. For the moment, she has persuaded the Democratic caucus in the House to follow this tack. But she knows that it alone is not enough to bring Trump down, or to effectively restrain him.

The second part of her strategy is a high-stakes gamble. It is to drive Trump nuts — to goad him into a series of breakdowns that will persuade enough of the public that he is not only unfit for office but also incapacitated for it. The trouble with this strategy is that it is Trump’s own game. He relishes slandering his opponents and mocking those who have served him, and he is completely unencumbered by principle, common decency and truth. In short, he is a masterful bully, and armed with the bulliest pulpit there is, the presidency. There is, however, one person Trump seems genuinely afraid of. It is the one person tough enough and confident enough to treat him not as a foe or an equal, but as a child, in the way a certain kind of mother deals with a particularly wayward child.

Nancy Pelosi, mother and grandmother and by far the shrewdest and ablest Democratic politician of her time, indeed the most powerful woman to ever hold public office in America, believes she is that person. Perhaps she is right. We will soon get a chance to see. Once more, as in the maneuvering last winter over the shutdown of the government, it’s the Don and Nancy show. Last week, emerging from a meeting with her caucus and just prior to one with Trump himself, Pelosi accused him of a generalized “cover-up” of his administration’s malfeasance. Trump scuttled the meeting, but he was reportedly so apoplectic over Pelosi’s remark that he felt obliged to parade five witnesses in public to attest that he had not lost his temper in a bizarre display of personal inadequacy.

The next day, Pelosi jabbed at Trump again, suggesting that he needed a crisis “intervention” by his family and that his cabinet consider invoking the Twenty-fifth Amendment to remove him from office. Again, Trump took the bait, dubbing Pelosi “Crazy Nancy.” But almost at once, he withdrew the epithet — much like a child who sees he has gone too far with his mother. Pelosi can’t do this every day. It might not work in the long run — or it might risk pushing Trump, quite literally, to the brink of a nuclear meltdown. But right now, it’s the one game in town.