Jim Geraghty posted an in-depth breakdown of the Toomey-Sestak race from a politico keeping his head on straight, despite a slew of polls showing a dead heat in the Keystone State. You can — and should — read the entire analysis for yourself, but for our purposes let’s just excerpt the Election Day scenarios:
Scenario One: Presume Pennsylvania’s turnout will be 36.5 percent Democrat, 37 percent Republican, 24.5 percent Independent. Applying these targets to Quinnipiac’s split yields a pretty easy to call 52.6 percent to 46.9 percent, or 5.7 point victory for Toomey. The way I came up with my splits is to take the 2008 Rate 44-37-17, and adjust based on Rasmussen’s summary of Party Affiliation percentage change in Nov 2008 versus Sept 2010.
Scenario Two: The problem with Scenario One is that while I capture the change of party affiliation, I assume a presidential year base model rather than a mid-term election. In a midterm turnout will be lower — 50 to 70% of a presidential year, which means only the more enthusiastic voters will turn out. Some expect this to be anywhere from 3 to 7 points — overall advantage to the GOP. My model takes a more conservative view with the Dems falling to 34 percent, the GOP up to 38 percent, and Independents to 28 percent. This gives Toomey a very comfortable 9 point win (and is consistent with many polls, with the same cross-tabs as Qunnipiac and PPP).
Scenario Three: But there is another problem with this assumption, which is the Tea Party as an affiliation. As noted, the GOP support has gone down since 2008. How is this possible? The emergence of the Tea Party. Tea Party Independents are going to vote and to be blunt, they will not be voting Democrat. Many of these voters also will not be telling any pollster they “are” Republicans. Going with a cruder model, but one that tries to capture the Tea Party, using flimsy data and guess-timates, I believe the Electorate in Pennsylvania is 34 percent Republican, 37 percent Democrat, 19 percent Tea Party-Independent, and 10 percent Moderate-Independent. Applying the Quinnipiac cross tabs where Republican and Tea Party have the same levels of support for Toomey, and where Moderate-Independents favor Sestak 53 percent to 47 percent yields . . . a 12 point Toomey win.
Thus I believe the margin race will end up between 9.1% and 12%, which is to say I will go out on a limb by taking the midpoint, and predicting Toomey beats Sestak by 10.5 percent.
Bottom line: nothing has changed with this race other than the pollsters’ predicted turnout models.
This does comport with what we’ve been hearing at Battle ‘10, and what has been demonstrated in the Public Policy Polling methodology: that the race is tightening only thanks to an oversampling of Democrats.