Below The Beltway

Andrew Sullivan looks at this collection of polls from RealClearPolitics:

And says this:

Just looking at this raft of polling data, it’s perfectly clear that Rasmussen is polling a different country than other polling outfits.

Umm, Andrew, perhaps not a different country, but maybe a different population:

The ABC News/WaPo results are based on a random sample of adults, the CBS News and Gallup results are based on a random sample of registered voters, and the Rasmussen results are based on a random sample of likely voters.

So, obviously, there’s going to be a difference, perhaps even a substantial one, between the poll numbers.

Instead of complaining about numbers he doesn’t like, Sullivan should be wondering why likely voters are seemingly so different from adults or mere “registered voters” when it comes to their opinion of the President and the Democratic Party.

Update:in the comments, it’s worth noting that a recent study of the 2008 election found Rasmussen to be the most accurate poll:

For all the derision directed toward pre-election polling, the final poll estimates were not far off from the actual nationwide vote shares for the two candidates. On average, preelection polls from 23 public polling organizations projected a Democratic advantage of 7.52 percentage points on Election Day, which is only about 1.37 percentage points away from the current estimate of a 6.15-point Obama margin in the national popular vote.

Following the procedures proposed by Martin, Traugott and Kennedy (see Public Opinion Quarterly, Fall 2006, pp. 342-369) to assess poll accuracy, I analyze poll estimates from these 23 polling organizations. Four of these polls appear to have overestimated McCain support (indicated with a * below), while most polls (17) overestimated Obama strength.

Pre-election projections for two organizations’ final polls—Rasmussen and Pew—were perfectly in agreement with the actual election result (**).

The following list ranks the 23 organizations by the accuracy of their final, national preelection polls (as reported on pollster.com).

1. Rasmussen (11/1-3)**
1. Pew (10/29-11/1)**
2. YouGov/Polimetrix (10/18-11/1)
3. Harris Interactive (10/20-27)
4. GWU (Lake/Tarrance) (11/2-3)*
5. Diageo/Hotline (10/31-11/2)*
5. ARG (10/25-27)*
6. CNN/Opinion Research (10/30-11/1)
6. Ipsos/McClatchy (10/30-11/1)
7. DailyKos.com (D)/Research 2000 (11/1-3)
8. AP/Yahoo/KN (10/17-27)
9. Democracy Corps (D) (10/30-11/2)
10. FOX News/Opinion Dynamics (11/1-2)
11. Economist/YouGov (10/25-27)
12. IBD/TIPP (11/1-3)
13. NBC/WSJ (11/1-2)
14. ABC/Washington Post (10/30-11/2)
15. Marist College (11/3)
16. CBS (10/31-11/2)
17. Gallup (10/31-11/2)
18. Reuters/ C-SPAN/ Zogby (10/31-11/3)
19. CBS/NY Times (10/25-29)
20. Newsweek (10/22-23)

Initial Report: November 5, 2008

In the end, I think it’s fairly clear that, for many people, the willing to accept the results of a particular poll usually correlate pretty nicely with whether or not that poll is good news for whatever side of the political debate they happen to be one.

Update # 2: It’s also worth noting that Nate Silver rates Rasmussen in the top three among pollsters, while ABC/WaPo is ranked # 16, CBS is ranked at # 30, and Gallup is ranked at # 25.