The polls are a bit of a mess right now, but the sources of disagreement seem a little clearer today. A big polling duel might be shaping up for November: Gallup and Rasmussen v. World. Before delving into details, let's not forget that the big picture is quite clear. If we simply ignored trendlines or the characteristics of the firms, an average of polls would show Obama clearly ahead nationally, probably by about four points, and clearly ahead in the big East Coast battlegrounds by a similar margin. Would there be a relatively big spread in the polls?
The tracking polls showed Obama remaining at elevated levels, but the Washington Post threw a wrench into a clear assessment of the race: The Washington Post showed Obama leading by 1 point among likely voters but 6 points among registered voters, a bounce of 3 points among likely voters and 7 points among registered voters. As a result, the gap between registered and likely voters actually widened after the DNC, presumably because Obama only swayed the views of unlikely voters without convincing them to turnout on his behalf.
With Obama holding a narrow but consistent lead in polls of registered voters, some have begun to speculate about whether Romney would seize the advantage once polls begin to apply likely voter models. While it's possible, recent polls suggest that Obama would maintain a slight advantage. As an empirical matter, Republicans do better among likely voters since the GOP draws from high turnout groups like seniors, while Democrats depend on constituencies with low turnout rates, like young voters and Latinos.
Mark Blumenthal of The Huffington Post, perhaps the best public resource on the intricacies of polling, has taken an inside look into the nitty-gritty details of Gallup's polling. The piece is a must read for polling junkies, but the short story is that defensible methodological choices lead Gallup to under sample non-white voters and produce marginally more GOP-friendly results than other pollsters.
Mark Blumenthal moderates a debate over the GOP's prospects for retaining control of the House. Basically, the historical evidence shows that it would be hard. Wave elections happen infrequently, and they're often a rejection a the incumbent party. It seems especially true in the last few decades that voters are motivated by revulsion against, rather than enthusiasm for, the incumbent party. All of that suggests Democrats won't have a big wave until Republicans hold the White House. But, there's an important caveat here: age.
Mark Blumenthal sums up the data: Any way you slice it, there does appear to be a real tightening of opinion on health reform although as always, these results are snapshots and subject to change.