The Colbert Report is broadcasting from Pennsylvania in the run-up to next Tuesday’s primary, and Hardball host Chris Matthews, himself a Philly native, stopped by for a chat last night. Matthews, perhaps still smarting after some rough treatment in a New York Times magazine profile last week, toned down his regular bombast, but his big mouth did let it slip that Hillary Clinton will be making an appearance on the Colbert Report later in the week—much to the chagrin of host Stephen Colbert. Matthews also made it pretty clear he’s planning on running for Arlen Specter’s senate seat in 2010, stopping just short of formally announcing his campaign. “Some people growing up … some kids want to be a fireman. I want to be a senator,” he claimed. The takeaway, of course, is that Matthews essentially admitted that he hasn’t grown up yet, but you knew that already.

Anyway, as his recent softball Hardball interview with Pennsylvania governor and potential vice-presidential candidate Ed Rendell proves, he’s already begun to butter up the right people.