Stephen Colbert called it "an announcement." Chris Matthews went on the Colbert Report last night and, responding to the host's importuning to declare his candidacy for US Senator from Pennsylvania, ultimately stated: "I want to be a senator." Over on MSNBC, Morning Joe played a clip of their colleague's appearance, then chewed it over. STEPHEN COLBERT: There's a lot of talk that you might be running for Arlen Specter's seat. Matthews first played it coy.