An MSNBC executive has announced that Chris Matthews won't be running for Senator from Pennsylvania, having told the Hardball staff of his decision earlier today.

Polling had shown Matthews in a tight race against GOP incumbent Arlen Specter, but Specter is hardly out of the woods. There is a good-sized bench of elected Democrats in Pennsylvania -- and on top of that, Specter could very well face a tough challenge in the Republican primary like he did in 2004.