That should never happen. A scandal should be able to lead to the removal of individual officials, but it should not reverse which party won an election. “If the electorate says that such-and-such a party should have the White House for four years, it ought to have the White House for four years,” Dwight Eisenhower wisely said.

The potential for a partisan reversal raises all kinds of problems. It creates incentives for one party to exaggerate a scandal (which, to be clear, is not happening in this case). It can also lead to more voters distrusting an impeachment process. “The whole point of having a line of succession is to ensure a smooth transition and a continuity of administration in a time of crisis,” my colleague Jesse Wegman has written. “Having a leader of the opposing party take over the White House, especially in an era of intense political polarization, would not achieve that, to put it mildly.”

Or as Jonathan Bernstein of Bloomberg Opinion writes: “It’s contrary to the entire structure of the constitutional system, which separates legislative from executive institutions and forces them to share powers.”

The line of succession stems from a 1947 law, and it can be changed with a new law anytime. Pelosi and House Democrats should pass such a law as soon as possible, so that every potential successor comes from the executive branch. It would be a victory for good government — and would also send a message about the severity of Trump’s and Pence’s high crimes and misdemeanors.

The Democratic debate

I was pleased to see that last night’s moderators didn’t ask about Medicare — an obsessive focus of the early debates — in any of their first nine questions. Pete Buttigieg brought up the subject, and the moderators asked a few follow-up questions. But they didn’t allow Medicare to dominate the debate. They found time for climate change, voting rights, China, the wealth tax and more. Nicely done, moderators — Rachel Maddow, Andrea Mitchell, Ashley Parker and Kristen Welker.