The Upshot’s model gives Mrs. Clinton an 88 percent chance of winning. It’s about the same probability of hitting a field goal from the 20-yard line.

That’s a pretty good way to think about it. If Mrs. Clinton ultimately wins, we will probably look back and say she had more or less already won it by this point. If she loses, these next two months will be talked about for decades.

The game-winning field-goal analogy has one big weakness: She may win this by a lot more than a field goal.

The possibility of a landslide victory for Mrs. Clinton — one larger than any since 1984 in the national popular vote — is larger than the chance that Mr. Trump will pull it out. According to The Upshot model, Mrs. Clinton has a better shot at winning the red state of South Carolina than Mr. Trump has at winning the presidency. In that sense, perhaps Mrs. Clinton’s position is more like having a double-digit lead at the beginning of the third quarter.