House Democratic leaders, following frustrated efforts to hold President Trump to account, understandably want to strike quickly to impeach him on the grounds of one extremely serious issue: his pressuring the president of Ukraine to get the goods on his Democratic rival Joe Biden. But they’re risking making their target too narrow and moving too fast.

In so doing they could end up implicitly bestowing approval on other presidential acts that amount to a long train of abuses of power. And going too quickly could shut off the oxygen that might fuel Republican acceptance that it’s time to break with Mr. Trump — perhaps enough of them to end his presidency.

To limit the impeachment process to the most blatant presidential misdeed yet discovered would leave in the dust — unresolved for history, setting dangerous precedents — the possibility of holding accountable a president who routinely enriches himself at the expense of the taxpayers and flouts the Constitution’s emoluments clause, lies so persistently that we’re far from the democratic concept of transparent government, usurps the role of Congress by unilaterally holding up funds or using them for other purposes than it has approved, bullies private businesses by threatening a tax increase or a significant raise in postal rates (as Mr. Trump did to Amazon, whose owner also owns The Washington Post), tells intelligence alumni who openly criticize him that he’ll suspend their security clearances and fights the law that allows Congress to obtain his tax returns.

Speaker Nancy Pelosi, a master strategist, has said that these issues can be taken up later. With respect, if a president were to be impeached more than once, what is the meaning of impeachment? Will Republican senators be willing to vote to eject Mr. Trump from the presidency, which is what the Senate trial is about, on the basis of one issue, no matter how repellent?