Majority PAC is going on the air in Pennsylvania for the first time, signaling that Democrats are concerned about Sen. Bob Casey's reelection bid.
Smart Media Group, a Republican media-buying firm, tweeted Tuesday afternoon that the Democratic super PAC has placed a $515,000 buy in Pittsburgh for October 24 to November 5.
Casey held a big lead over his opponent, self-funding businessman Tom Smith, over the summer. But recent polls have shown the contest narrowing, and a Quinnipiac poll last week showed Casey's lead at just three points.
Casey will certainly be outspent in the race: Third quarter fundraising reports indicated that Smith has dumped a total of $17 million into his bid to unseat the senator. Casey raised $1.5 million in the quarter and finished September with $5.2 million in the bank. Smith had $7 million, and presumably is willing to put in more money as needed down the home stretch.