Fred Thompson, who challenged John McCain for the Republican presidential nomination, cast his former rival Tuesday as a man of integrity with the will to shake up Washington.

The former Tennessee senator and actor also sought to rally the party faithful behind McCain's running mate, Alaska Gov. Sarah Palin. Palin has faced intense scrutiny this week after a series of personal and political revelations, including news that her unmarried teen daughter is pregnant and the disclosure that she had backed federal funding for a controversial bridge in her state that McCain and others had held up a symbol of pork-barrel spending.