Multiple polls now show that in the aftermath of Sestak's first paid media blitz, the congressman has come within single digits of the former Republican senator in their Democratic primary in two weeks.

A Quinnipiac poll today shows Specter leading 47-39, and polls from Rasmussen and Muhlenberg College also show him within single digits. 

Quinnipiac's numbers are particularly noteworthy, given that they showed Specter leading 53-32 a month ago. Since then, however, Sestak has begun to unleash his $5 million war chest, and it appears to have paid some dividends.

But much is yet-to-be-determined. Nearly half of voters don't know Sestak well enough to rate his favorability, while Specter is almost universally known.

Look for this race to get dirty in the short time before the May 18 primary. Specter is known as a brawler, and he's got a fight on his hands.