In yesterday's Senate primaries in Arkansas and Pennsylvania, turnout and shifting vote patterns left sitting Senator Blanche Lincoln (D-Ark.) facing a runoff and defeated Sen. Arlen Specter (D-Penn.).
The Arkansas' contest this year drew more voters than the state's 2008 presidential primary (with 99 percent counted, 326,216 have voted, compared with 314,234 in the '08 contest) and also topped the 1998 Senate primary (318,801 voted then). In that contest, Lincoln won the right to a runoff against then Attorney General Winston Bryant. She matched her overall share of the vote in that contest (45 percent), but there are some significant geographic differences.
Lincoln lost a large share of the vote in the state's eastern region - a mostly rural area with a large black population. In her first run at the Democratic nod for the Senate, Lincoln won 64 percent of votes there, but this time around, she garnered just 45 percent of the vote to Lt. Gov. Bill Halter's 42 percent. This region also represented a larger share of the vote than in 1998 - 29 percent vs. 22 percent.
But in the rest of the state, Lincoln improved her margins, including a 10 point increase in the state's most politically conservative region (the northwest) and more modest bumps in Little Rock (up four points to 49 percent, her largest regional tally) and the traditionally Democratic south (up six points).
The third challenger in yesterday's contest in Arkansas, businessman D.C. Morrison, topped out at 16 percent of the vote in the southern slice of the state.
Turning to Pennsylvania, as Paul Kane notes, Rep. Joe Sestak's win over Specter mirrors the pattern seen when Hillary Clinton topped Barack Obama in the presidential primary there two years ago. But there are a few notable differences between the two contests.
Sestak's home court advantage in the Philadelphia suburbs boosted him to a bigger margin there than Clinton (57 to 43 percent for Sestak in this race, 51 to 49 percent for Clinton in the presidential primary), while he garnered smaller margins in the northeast (Clinton won 66 percent of votes there to Sestak's 56 percent) and the western part of the state (Clinton had 62 percent, Sestak 56 percent).
Though Specter mirrored Obama's two-thirds share of the vote in Philadelphia, turnout there among registered Democrats was lower than in the rest of the state (as of now, with 96 percent of the votes in Philadelphia counted, 20 percent of Democratic registered voters cast a ballot, compared with 25 percent in the rest of the state, where 99 percent have been counted).
It's also worth looking at Specter's performance in the 2004 Republican primary, when he faced off against a challenge from the right in Pat Toomey. In that contest, Specter prevailed by winning big in Philadelphia and its suburbs, and holding a narrow edge in the rural, central parts of the state known as the "T."
But the distribution of votes in a Republican primary is vastly different from a Democratic one. In the GOP contest, just 4 percent of votes came from Philadelphia, while in this race, it was 16 percent. And that central region represented 42 percent of voters in the Republican primary, but in this contest, just a quarter of votes came from the state's geographic center, and Specter was unable to hold his edge there. Sestak topped Specter 60 to 40 percent.