What a difference a week makes! When we looked at the model on Monday, September 26, (the day of the first presidential debate), Hillary Clinton’s odds of winning were 64 percent. There had been some subtle improvements in the previous week in Clinton’s national polling numbers (as Pneumonia-ghazi started to fade from view) but that hadn’t really trickled down into the state-level polls, which is what our model is based on. By Thursday, September 29, that improvement was starting to filter into the state polls, and our model ticked up to 68 percent … but that was still based only on polls with a pre-debate field period.
On the morning Monday, October 3, we had a few post-debate polls under our belt … and Clinton’s overall odds were up to 72 percent … but we were still left wondering why everything was so quiet on the polling front. By the end of Monday, though, the deluge had arrived, and with one exception (Quinnipiac’s Ohio poll), everything was very good news for Clinton: among others, a Clinton +11 poll from Monmouth in Colorado, another Clinton +11 poll in Colorado from Keating Research, polls from Quinnipiac with Clinton +5 in Florida and +3 in North Carolina, a Clinton +9 poll in Pennsylvania from Franklin & Marshall, a Clinton +3 poll in Nevada from Hart Research, and a Clinton +7 poll in Virginia from Christopher Newport Univ.
It may well have been her single best polling day of the cycle, and by Tuesday her odds had jumped to 82 percent, a one-day gain of 10. That matches the largest single-day gain our model has seen since we started running. That other gain of 10 happened between August 8 and 9; in case you’re wondering what was happening then, that was the Monday after the Democratic convention ended, when the post-DNC polls started to show up. So you could say that the debate was one of the most momentous events of the campaign: if your metric is the effect it had on our model, she got a convention-sized bounce out of it.
The subsequent days have seen even more strong poll results, most notably two different polls on Wednesday (from Monmouth and Anzalone Liszt) giving Clinton a 2-point lead in Ohio, which isn’t a lot but serves to counteract the Quinnipiac poll that had her down 5. The subsequent polls weren’t enough to really move the model much higher; it currently places Clinton’s odds at 83 percent. But they do continue an impressive little winning streak: out of the several dozen polls of swing states released since the debate, only one of that entire stack had Donald Trump leading (again, that Quinnipiac Ohio poll). And that stack covers every major swing state except Iowa (and Wisconsin, if you even consider that a swing state in the first place).