Donald Trump now trails Hillary Clinton by 6.6 percentage points, according to our polls-only model. And the clock is ticking. We’re 26 days from the election, and by this point in past campaigns, the concrete had basically dried.

Trump could stage a comeback. It’s possible. But it would be basically unprecedented.

Back in August, after the conventions, I wrote an article saying that while Clinton was a heavy favorite — she led Trump by between 6 and 8 percentage points — the race was far from over. We had plenty of historical examples of races shifting by more than 6 points, even after the political conventions. Since 1952, half of the races for which we had polling after the conventions featured shifts of 5 percentage points or more. Some elections, such as 1968, 1976 and 2000, looked like they could be near or total blowouts, but ended up being rather close.