The polls

Kevin Drum takes Nate Cohn’s analysis and adds some of his own:

As I mentioned last night, Hillary Clinton really is significantly ahead of Donald Trump in the national polls. She’s ahead by about four points, and that’s a pretty normal winning margin in a presidential election with no incumbent running. In the New York Times, Nate Cohn says the same thing but with a lovely little graphic to make his point:

Her lead is smaller than it was last month….But she retains an advantage — perhaps by 4 percentage points nationwide, and a similar margin in the battleground states that are likely to award the electoral votes needed to win the presidency. This straightforward story can get lost in the headlines, which tend to give the most attention to the most surprising results — whether it’s a predicted Clinton landslide or a narrow lead for Mr. Trump in key states.

The truth is probably somewhere between those extremes. Pollsters aren’t joking about the “margin of error”: the inevitable random variance in polls that exists simply by chance. If Mrs. Clinton leads by 4 points, you should expect polls that show her with a big lead or locked in a tight race, with others clustered around the average. That’s more or less what we saw this past week.

As Cohn says, individual polls are likely to fall on a bell curve. I’ve recreated his chart below, with actual recent polls in red. As you can see, it’s all perfectly normal (pun intended).

And, yeah, she’s come down to about 69%, but the money is still on Clinton.

ADDENDUM:

Went back and read Cohn more closely after posting this.  And a couple points I wanted to add:

While the occasional poll has looked good for Mr. Trump, it has been two months since he led a national survey that included voters without a landline telephone. Mrs. Clinton has led dozens.

Whoa!  Sure, landline polls do what they can to statistically account for this, but there’s only so much you can do.  For now, I stubbornly remain one of those landline people.

Also…

In general, the polls are far more predictive of the final results a few weeks after the conventions than they are immediately before. No modern presidential candidate who trailed in the polls several weeks after the convention has come back to win the popular vote. This isn’t to say it couldn’t happen, especially if the post-convention polls were fairly close. There have been instances in which the polls have moved considerably after the conventions, even if they didn’t contradict the result of the popular vote (as in 1976 and 1980).

But it does indicate that a post-convention lead is quite meaningful, even with weeks or months to go until the election. By that time, both candidates will have had many and fairly equal opportunities to unify their parties and make their cases to the broader electorate. If a candidate holds a clear lead at that point, it means a lot.
Yeah, so like I’ve been saying.  Patience, young grasshopper.
Advertisements

About Steve Greene
Professor of Political Science at NC State http://faculty.chass.ncsu.edu/shgreene

2 Responses to The polls

  1. ohwilleke says:

    My family ditched the landline after something like 95% of calls we received were junk calls anyway. Now, we have four phone numbers for four people and use are abandoned landline number for loyalty cards and car salesmen.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: