The critical element that skews likely voters more Republican this time is that likely voters = engaged voters, engaged voters skew older, and older voters skew McCain in this race.
Marc Ambinder explains:
Based on data, studies and experience, pollsters assume that older voters tend to reach information saturation earliest, tune in the earliest, and pick their candidates the earliest. Likely voter models this far out don't oversample older voters per se -- they oversample voters who have made up their mind and aren't likely, even if they say they're likely, to change their minds. John McCain's leading among older voters, but not by much. So when younger voters -- younger than 65 -- begin to make up their minds in the fall, likely voter models will move back into equilibrium and Obama's lead among registered voters should begin to match his lead among likely voters.Chuck Todd-led First Read agrees:
[R]ight now, pollsters will tell you that with older voters leaning McCain these days, any likely voter model is going to favor McCain for now. If Obama moves younger voters as well as many observers assume come October, the likely voter numbers could change.However, a key assumption needs to be called into question. This year, are the engaged voters skewing older? Are older voters reaching information saturation the earliest? Pew finds a surprise for pollster likely voter assumptions:
Compared with previous election cycles, voter engagement is up among all demographic groups, but has increased more among voters under age 50 than among older voters. Uncharacteristically, the youngest voters -- those under age 30 -- are at least as knowledgeable, and in some cases more knowledgeable, about candidates' positions on Iraq and abortion than are older voters.The assumption reported by Ambinder and Todd is that younger voters will be making up their minds closer to the election and that this will change the likely voter screen at that time. In other words, the pollsters are correct now (but not predictive of November) and they will also be correct in October (and predictive of November) when they expand their likely voter screen. All we are waiting on is the young voters to tune in and make up their minds (presumably skewing things back toward Obama).
This predicted dynamic flies in the face of the evidence. Pew reports two unprecedented findings in their poll. First, Democrats are expressing stronger interest in the campaign than Republicans for the first time since Pew began tracking in 1992. Second, the percent of voters more interested in the campaign relative to four years ago (usually hovering near 50% across the board) shows a huge jump on the Democratic side to 71%.
If engagement and interest is what makes a voter a likely voter, and if younger voters have reached saturation ahead of older voters reflected in their superior grasp of information, then any likely voter screen that doesn't currently skew Democratic is probably an incorrect likely voter screen.