The political climate has changed at home for Sen. Arlen Specter (PA), the Republican-turned-Democrat who represents a crucial swing vote in the Senate: a Quinnipiac poll today shows him virtually tied with Republican rival Pat Toomey, leading 45 percent to 44 percent. Before Specter switched parties in late April, the conservative Toomey was mounting a primary challenge on Specter from the right, and it looked like Specter would go down in primary defeat. And that was part of the reason Specter switched. Once he became a Democrat, Specter instantly crushed Toomey in general election polls of Pennsylvania's total population of likely voters, a more moderate crowd than those who would have decided his fate in a Republican primary. As Quinnipiac notes, he led Toomey 53-33 on May 4. His closest competion then came from the left, in the form of Rep. Joe Sestak, a Democratic candidate who challenged Specter's Democratic credentials.

The question here is whether new pressure from Toomey will change Specter's vote in the Senate. Before his switch, people speculated Specter would run to his right, covering himself against Toomey's criticism and appealing to conservative GOP primary voters; afterward, observers wondered if he'd vote more liberally, given the challenge from Sestak. Specter is fiercely independent; he ardently maintains his freedom from partisanship and political pressures. There's a question as to how much this sort of thing affects his stances on critical issues, but he represents an important vote on almost any close issue that needs 60 votes in the Senate, notably health care and the Employee Free Choice Act, backed by labor unions, which play a significant role in Democratic politics in Pennsylvania.

Insofar Specter "runs" anywhere, today's poll marks yet another reversal in the pressure that's on him: in today's poll, he bests Sestak 55 to 23, but Toomey looks like a legitimate threat.

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