But as you said, it’s best to focus on the average. Right now, the balance of data remains consistent with a modest Clinton lead. A single high-quality poll showing a tied race isn’t enough to change that: If Clinton is up by, say, 3 or 4 points, you would expect a few high-quality polls to show a very tight contest, while others would show a larger Clinton lead. It’s also possible that the NYT/CBS result is dead-on, and a wave of new data will confirm a closer race than the balance of recent evidence.

I’m not sure we’ll get to find out, since the convention is just around the corner.

Toni This is the speculative part of the program. Her lead is shrinking. Why?

On the one hand, you have the rebuke from the F.B.I. director over the emails, and you also have a calamity in which an African-American killed five police officers in Dallas amid a sense of racial strife. On the other hand, Bernie Sanders endorsed her, although that was very recent (so it wasn’t captured by the polling).

Nate Well, I think the F.B.I. is the easiest explanation. I wouldn’t discount racial tension, either. I’d note that Obama’s approval rating in Gallup dipped to 48 percent today, the lowest in a while. I’ll be interested to see whether other polls show that, too.

Toni Stating the obvious, but there are more whites than African-Americans, so black-white strife is not normally a political winner for Democrats. When we talk about whites favoring Trump, we tend to skip the explanation. Republicans have won whites for decades, but readers should take a look at Nick Confessore’s article for how Trump is taking white identity politics to a new level. Or read Jamelle Bouie in Slate, who’s been writing about this a lot.

Nate I certainly agree that racial polarization would be bad for the Democrats. But Trump isn’t doing much better than Mitt Romney among white voters, if at all. He’s losing as many well-educated white voters as he’s gaining among less educated white voters.

I think Clinton’s polling numbers may be particularly vulnerable to these sorts of fluctuations in the media environment. She’s counting on the support of a lot of people who simply don’t like her very much. I’d guess a lot of them know, deep down, that they’ll support her eventually. But right now, the act of telling a pollster that they intend to support someone they don’t really want to support might be fairly agonizing.