Six weeks ago, I pointed out that Romney’s favorability numbers, net, were not much worse than President Obama’s. Yet the fans of the president have clung — bitterly? — to the notion that Obama’s personal likeability would be the difference-maker in this year’s presidential election.
Note that among registered voters in the new ABC News/Washington Post poll, Obama’s favorable/unfavorable split is 49 percent favorable, 48 percent unfavorable; Romney gets 44 percent in both favorable and unfavorable.
Among all adults, President Obama splits a better 52/45, and Romney’s at 41/45. ABC News didn’t apply a “likely voter screen” to their numbers.
If you look closely at Obama’s job-approval rating, he’s right around 50 percent in the Real Clear Politics average. . . but if you look at just the polls of likely voters, he’s a bit lower: 49, 44, 48, 45.
If and when pollsters apply a likely-voter screen to their poll results, the numbers are likely to look a couple of points better for Mitt Romney and the Republican candidates this cycle.
Back in 2010, Nate Silver wrote:
Likely voter adjustment.
We now notate whether each poll is of likely voters, registered voters, or all adults, and include variables for this in the regression analysis we use to calculate pollster house effects. The regression shows that, holding house effects constant, Democrats do a net of 4 points better in polls of registered voters (with a 95 percent confidence interval of about 2-6 points) than in polls of likely voters, and roughly 7 points better in polls of all adults.
So if we took, for example, the recent Ipsos poll of California, a poll of registered voters which showed Barbara Boxer with a 4-point lead over her Republican challenger, Carly Fiornia, we would expect it to show about a tied race if a likely voter screen had been applied instead. The adjustment works in exactly this fashion: it adds a net of 4 points to the Republican candidate’s margin each time that it encounters a poll of registered voters, and 7 points every time that it encounters a poll of adults (which is very rare in state-level polling). Polls of likely voters are left unchanged as having a likely voter screen is assumed to be the default condition.
Of course, 2010 was a great year for Republican voter enthusiasm and a pretty lousy one for Democrats’ enthusiasm; this cycle will probably have both parties with at least moderate enthusiasm. But it’s pretty clear that Obama’s poll numbers — in job approval, favorability, and head-to-head matchups with Romney — are being held aloft by support from people who are unlikely to be voting in November.