On Friday, Oct. 28, James B. Comey, the F.B.I. director, sent a letter to Congress about new evidence in the investigation into Hillary Clinton’s emails. Politicians, analysts and journalists are still debating whether the letter cost Mrs. Clinton the presidency. It’s certainly possible. But I am not at all sure, in part because of the final Upshot/Siena College poll in Florida.
I had learned the results of our survey that morning. It showed Donald J. Trump ahead of Hillary Clinton in the state by four percentage points, 46 percent to 42 percent.
At the time, the poll looked like a bust. There wasn’t much reason to think the result was even in the ballpark. Mrs. Clinton was ahead by six points in national polls and ahead by a similar margin in states worth 270 electoral votes, suggesting Mrs. Clinton was probably up by a few points in Florida. I can’t say I was thrilled about having to write an article about a poll that looked flat-out wrong.
But it’s now clear that Mrs. Clinton was weaker heading into Oct. 28 than was understood at the time. Several other polls were conducted over the same period that showed Mr. Trump gaining quickly on Mrs. Clinton in the days ahead of the Comey letter. And the timing of these polls — particularly the gap between when they were taken and when they were released — has probably helped to exaggerate the effect of Mr. Comey’s letter on the presidential race.