Joe Biden leads Donald Trump in Pennsylvania and Florida, according to new Times/Siena polls taken after the first debate.
Biden leads in Pennsylvania, 49 to 42 percent among likely voters. He leads in Florida, 47 to

In an analysis of interviews conducted yesterday, including in Arizona (where a poll is ongoing), there was modest evidence of a shift in Joe Biden's direction after Trump's COVID diagnosis. That said, one day of interviews is not nearly enough to reach any firm conclusions

The shift, though, would be material if confirmed and it was statistically significant, controlling for the demographic and political variables used in weighting. That said, it's still just one day of interviews. We'll have to wait and see here.

Of the two results, the biggest surprise was probably Florida, where we found Biden+5 with a R+4 sample. This is a fully updated voter file that reflects some meaningful GOP registration gains in the states.

It's just a subsample, so big MoEs here, but we found no evidence of the big Trump gains among Hispanic voters in Florida or in Miami-Dade County. Biden even narrowly led a (very small) sample of Cuban voters; they were R 47-28 by registration. Again, small samples but...

Some early theories on went went wrong with the pre-election polling this

Before we go into what went wrong, let's just call a spade a spade here: this was a bad polling error. It's comparable to 2016 in size, but pollsters don't have the excuses they did last time.
This year's polls would have been *way* worse than 2016 with a 2016 methodology

There are really two halves of polling: the quality of the sample you get, and the adjustments you take to improve the representativeness of your sample.
Since 2016, pollsters got better at the adjustments, but the underlying sample got worse

To my mind, the easiest way to see it: the crosstabs on white voters nationwide, particularly whites without a degree
In 2016, the polls *did* show Trump doing way better among those voters.
In 2020, they did not. And they were dead wrong.
Same story with seniors.

So what happened? How did the samples get that much worse over the last four years, especially among white voters without a degree and seniors?
At this stage, it's really just speculation. We'll know more later--it's too early for an autopsy.
But here's some early speculation