Democrats in Washington have officially entered the spending fray in the 2010 Senate lanscape, as the Democratic Senatorial Campaign Committee has launched its first independent-expenditure campaign. Their target: Pennsylvania, and Republican candidate Pat Toomey, who is polling ahead of Democrat Joe Sestak by four percentage points.

From Hotline OnCall's Reid Wilson:

The DSCC is spending $404K to air the ad on statewide broadcast and another $48K for cable spots, according to a source who follows political ad spending. That equals 300 gross ratings points in Philadelphia, 400 in Pittsburgh, 300 in Harrisburg, 600 in Wilkes Barre and 500 points each in Johnstown and Erie.

Dems are becoming concerned that several ads attacking Rep. Joe Sestak (D) are beginning to have an impact. Sestak is still refilling his coffers after an expensive primary in which he defeated Sen. Arlen Specter (D), but he's being outspent on TV by Toomey, the Chamber of Commerce and other right-leaning groups.

Here's the ad the DSCC is airing: