Word of Sen. Arlen Specter's party change spread quickly in the Pennsylvania capitol.
Republican Party chair Robert Gleason says he's "deeply disappointed" by the move, charging Specter with putting his "political ambitions first."
Republican challenger Pat Toomey says Specter's switch makes sense, arguing he's "more at home in the Democratic party" than he was in the GOP.
Democrats, however, are already rallying around Specter.
State Rep. Josh Shapiro had been viewed as a contender for the nomination, but says he's no longer going to run.
State House Majority Leader Todd Eachus agrees, saying Specter needs to be the party's standard bearer.
Scott Detrow reports for member station WITF.