Think about election night: The returns that are available by midnight, say, will be heavy with in-person votes, and they might show that Trump is leading in enough states to win an electoral college majority. The president, bolstered by these initial returns, might declare victory. But until the mail-in votes are counted in key swing states, such a declaration could be premature.

“This will be an election like no other,” cautioned Steve Kornacki, the national political correspondent for NBC and MSNBC. Tempers will be high, and so will uncertainty about the result.

David Chalian, the political director at CNN, explained: “If someone out there is claiming victory, and we haven’t counted the vote yet and made a call, we have to be clear that the facts don’t back up that claim. . . . One thing that’s critical is that we be as transparent as possible about what is and isn’t in the vote count, and what we know about the still-outstanding vote.”