Roll Call has the story on the "game of ad buy chicken" between the National Republican Senatorial Committee and the Democratic Senatorial Campaign Committee in Pennsylvania and other swing states. Here are the details on Pa:

In Pennsylvania, the DSCC reserved $5.7 million, $1.5 million of which has already been spent. The NRSC has $2.5 million reserved for the open seat race between Rep. Joe Sestak (D) and former Rep. Pat Toomey (R). Toomey has led by at least 9 points in three of the previous four public polls released.