The race for Ohio is slowly tightening, but Mitt Romney does not hold a lead in a single poll in the current Real Clear Politics average (he is tied in two). Two polls from Time and CBS/Quinnipiac have grabbed headlines by showing Obama a five-point lead in each. Romney is chipping away at Obama’s poll lead, but the Democratic advantage in party-ID has increased across these polls. When looking at the polls in Ohio, it is becoming entirely possible that Mitt Romney should be able to win Ohio without ever showing a consistent lead in the polls, or any lead at all.
In the past week Romney has trimmed four-tenths of a point off of his deficit in the RCP average, going from 2.5 to 2.1, but at the same time, the average party-ID advantage for Democrats in these polls has risen from 5.5 to 6.5. A big reason for the increase in Democrats’ share in the polls is due to early voting. If a pollster calls someone who says they voted already, they are automatically passed through the likely-voter screen since they have, after all, voted. The problem with this can be best summed up by Gregory House: “Everybody lies.”
Pollsters can only work with what their respondents tell them, and this is the reason that likely-voter screens can be so tricky, though important, in polling. The preferable response is that you are going to vote or, in the case of Ohio, that you’ve already voted. Many respondents will say they are going to vote (or have voted) when in fact they may not end up doing it (this effect is known as social-desirability bias). For this reason, some likely-voter screens ask about previous elections and general political enthusiasm to gauge the actual likelihood that a voter will end up in the booth on Election Day. But that is where early voting throws the screen out the window — if a voter says they voted, there is nothing a pollster can do to but assume that it’s true. ...
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