On Tuesday evening Nancy Pelosi made one of the most colossal blunders in the modern history of American electoral politics. Rejecting the accumulated wisdom of a long and successful career in the House of Representatives, she set aside her own instincts and announced the beginning of formal impeachment proceedings against President Trump on the basis of a third-hand rumor about a phone call with the president of a Eurasian republic.

Pelosi knows this will not be popular. She knows more than that. She knows that it will be a disaster for the Democratic Party, that it will inflame the president's base and inspire even his most lukewarm supporters with a sense of outrage. She knows that in states like Michigan, upon which her party's chances in 2020 will depend, the question of impeachment does not poll well. She knows, further, that Joe Biden will not be able to spend the next 14 or so months refusing to answer questions about the activities of his son, Hunter, in Ukraine, and that increased scrutiny of the vice president's record in office will not redound to his credit. She and her fellow Democratic leaders had better hope that someone like Elizabeth Warren manages to steal the nomination away from him before this defines his candidacy the way that Hillary Clinton's emails and paid speechmaking did during and after the 2016 primaries.

Why? Because her hand has been forced. The same members of her caucus who have clamored for Trump's impeachment on the basis of his immigration policy, his non-existent collusion with Russian authorities during the last presidential election, and his ownership of various hotels have once again lighted upon high crimes and misdemeanors. While it is probably clear to some other members of the party's leadership that impeachment is a non-starter — not only because it is unpopular but because it will go nowhere in the Senate — the feeling seems to be that they have no other choice. Too many younger Democrats whose own political fortunes do not depend upon the party's national appeal, much less its control of the White House, have been allowed to control the conversation. Some of them are cynical, others merely naïve, but the takeaway is the same regardless: The hydra is eating its own heads. Pelosi should have known better than to feed it in the first place.

Where is all of this headed? In her press conference Pelosi bandied idle threats, but she knows she cannot enforce them. She also knows, surely, that she did not need to make them in the first place. Trump has made an end run around the Democrats by announcing that he will release a transcript of his phone call with Volodymyr Zelensky on Wednesday morning. If there is nothing in the text that justifies the perfervid speculation of his liberal enemies — and it is impossible to imagine his agreeing to its release if there were — it will not be possible to retreat from the opening of impeachment proceedings without embarrassment.

This does not mean that Pelosi will not attempt to do so regardless. It still seems to me supremely unlikely that this will ever make it to the level of introducing actual articles of impeachment, much less to an actual up-and-down vote on the question of impeachment. Every stalling tactic imaginable — not least among them the expansion of the inquiry to include avenues explored previously, such as the special counsel's findings, and new ones of whose lunacy we can only dream — will be employed. But this will not be enough to satisfy members of her caucus who will complain that the process is not moving along swiftly enough and would do so even if Trump were finally impeached. The business will never be put to bed until Donald Trump leaves office.

The only lasting effect of Pelosi's capitulation on Thursday will be making the latter unlikely to happen before 2025.