Nate Cohn

Nate Cohn @Nate_Cohn

Let's take an extreme example to illustrate: suppose a 50-50 race with *100%* turnout, and suppose 100% of Party A votes early, while no one in party B votes early. That poll will be biased toward party A, unless it assigned 100% turnout to all of party B (which wouldn't happen) — PolitiTweet.org

Nate Cohn @Nate_Cohn

Random thought: a lopsided Democratic edge in early voting may be a bit of an underrated challenge for pollsters. It's a bit dangerous to have one party lock in its votes, while the other party's voters don't get that kind of boost in their turnout probability — PolitiTweet.org

Nate Cohn @Nate_Cohn

@nickgourevitch We could get COVID under control if Beyonce would finally improve her image... — PolitiTweet.org

Nate Cohn @Nate_Cohn

@nickgourevitch We would get COVID under control if Beyonce would improve her image... — PolitiTweet.org

Nate Cohn @Nate_Cohn

RT @nickgourevitch: @Nate_Cohn Correlation is clearly causation right here. If you are favorable to Beyonce: 88% support/11% oppose a mask… — PolitiTweet.org

Nate Cohn @Nate_Cohn

@nickgourevitch ok now what about beyonce fav x mask wearing — PolitiTweet.org

Nate Cohn @Nate_Cohn

@howtoraiseajerk https://t.co/V8WdZf2CbK — PolitiTweet.org

Nate Cohn @Nate_Cohn

RT @Brand_Allen: @Nate_Cohn Really begs the question of why anyone would use RCP when there's @FiveThirtyEight. — PolitiTweet.org

Nate Cohn @Nate_Cohn

Anyway the polling drought will come to an end. Virtually all will want to weigh in before the DNC, which starts 8/17. In fact, that's the reason for the drought: if you're polling next week, you wouldn't poll over the last few. So I'd guess we've got a lot coming. — PolitiTweet.org

Nate Cohn @Nate_Cohn

The live interview state polls are also rare, and they don't add a ton of extra clarity. IMO, two Monmouth polls of GA/IA were maybe more like Biden+8 than their prior Biden+12 national result. Those Quinnipiac polls, OTOH, sure look like their last Biden+15 poll. — PolitiTweet.org

Nate Cohn @Nate_Cohn

So while I think the data is consistent with tightening, I don't think it disproves stability either. It is entirely possible that another round of round of ABC, Monmouth, CNN type national polls would show double-digit leads for Biden and move the average quickly back his way — PolitiTweet.org

Nate Cohn @Nate_Cohn

But the online polls show *very* little movement, and there are really no live interview polls at all--that big drop is mainly due to one poll, and may or may not hold up with more data. The real movement here is on the IVR side, both in terms of relative weight and trendline — PolitiTweet.org

Nate Cohn @Nate_Cohn

At the same time, none of this means that there *hasn't* been tightening. If we go back to this chart, there's still tightening across all mode. https://t.co/wKMqRJIOsh — PolitiTweet.org

Nate Cohn @Nate_Cohn

Now I'm not saying that the House Effects *should* be calibrated at A+ = true and adjust all others to it. My main point is that if there were as many Monmouth polls as Morning Consult or something, you'd have a different House Effect adjustment too — PolitiTweet.org

Nate Cohn @Nate_Cohn

Here, for instance, are House Effects by 538 pollster rating (where 0 is their "A+" and 1 is an "D-") As you can see, there's a decent relationship between pollster quality and a Biden House Effect. The small number of A+ polls means they can't anchor the adjustment. https://t.co/5Cu9D19DLu — PolitiTweet.org

Nate Cohn @Nate_Cohn

As a result, it's not like the House Effect drag Rasmussen all the way back to the live polls. Instead, it drags Rasmussen back toward the average, which is something more like a Morning Consult and YouGov. Similarly, a Monmouth poll would be adjusted back to the right. — PolitiTweet.org

Nate Cohn @Nate_Cohn

Another thing that rigorous averages do is adjust for 'house effects'--persistent bias in a poll. But these house effects don't go as far as you might think, since they're calculated with respect to the quality weighted average--which still includes a *ton* of non-live polls — PolitiTweet.org

Nate Cohn @Nate_Cohn

You can see that we have these moments in mid-July and mid-June when the live polls rise to nearly match the online polls. But right now, they're only about 15% of the estimate, even though they're considered the best polls. — PolitiTweet.org

Nate Cohn @Nate_Cohn

The rigorous polling averages--like the one you see here, or FiveThirtyEight--do give more weight to the live interview polls. But there's only so much you can do. Despite those efforts, IVR polls would probably still have more weight in the average--the live polls are too old https://t.co/5LROtpWhcv — PolitiTweet.org

Nate Cohn @Nate_Cohn

Here, for instance, is what the poll averages look like if you break the polls down by method. Black = all; blue = live; red = online; green = IVR. The live interview average is still at Biden+9.4, with the drop below 10 attributable to the one live poll of the last two weeks https://t.co/jchbxstqvN — PolitiTweet.org

Nate Cohn @Nate_Cohn

One reason is a change in the composition of recent polls. There's just one live interview national survey among the last *50* recorded by FiveThirtyEight. And in June/July, live interview surveys were quite a bit better for Biden than the others. — PolitiTweet.org

Nate Cohn @Nate_Cohn

One major reason is a change in the composition of the recent polls. There's only one live interview survey among the last *50* recorded by 538. — PolitiTweet.org

Nate Cohn @Nate_Cohn

So, even a 'simple' RCP-like average should obviously be better for Biden than this. But even if we add in all the recent polls to make a better RCP-like average, we'd still find Biden doing worse than earlier in the month. — PolitiTweet.org

Nate Cohn @Nate_Cohn

RCP is a particularly peculiar case. Yeah, it's a simple polling average, but even a simple poll average would include the Morning Consult and Ipsos polls. There's no plausible reason to exclude those but allow Rasmussen and HarrisX or whatever. — PolitiTweet.org

Nate Cohn @Nate_Cohn

Let's talk about what's happening under the hood on some of the poll averages right now https://t.co/AH2LeCvzoL — PolitiTweet.org

Nate Cohn @Nate_Cohn

MO02 as a tossup is quite consistent with a single digit presidential race in the state, which we've seen in a few polls now https://t.co/a75LGMJopI — PolitiTweet.org

Nate Cohn @Nate_Cohn

RT @Redistrict: New at @CookPolitical: five more House rating changes today, including four in Democrats' direction - and two veteran House… — PolitiTweet.org

Nate Cohn @Nate_Cohn

@RachelBitecofer @cfbarry486 @NiskanenCenter @ElectionWsphr you're really just going to respond to this with I should have promoted you more? this is a serious charge — PolitiTweet.org

Nate Cohn @Nate_Cohn

@RachelBitecofer @cfbarry486 @NiskanenCenter @ElectionWsphr you're really just going to respond to this allegation with I should have promoted you more? this is a serious charge — PolitiTweet.org

Nate Cohn @Nate_Cohn

@RachelBitecofer @cfbarry486 @NiskanenCenter @ElectionWsphr i think you owe a serious explanation of the... disconnect... between how you've characterized your forecast and what it actually appeared to show. if you think it's a misrepresentation, i think you need a better explanation than 'tossup didn't mean tossup' — PolitiTweet.org