Republicans are craving an authority figure, an authoritarian authority figure, and Fred Thompson has played in the movies a White House chief of staff, a director of the Central Intelligence Agency, a highly placed F.B.I. agent, a rear admiral, numerous military brass, a senator, and (at least twice) president of the United States. He's the go-to guy for projecting governmental power -- absolutely perfecto, in other words, for the Party of Smaller Government!
He also has incurable non-Hodgkin lymphoma, an "indolent" form of the cancer that so far has been treatable with Rituxan.
He used to be a crusader against governmental corruption. Back in the late 1970s he helped bring down Tennessee Gov. Ray Blanton for selling prison pardons, and of course he's the dude that got to ask Alexander Butterfield, "Are you aware of the installation of any listening devices in the Oval Office of the President?"
Conservatives want to make him over as an arch-conservative, and Mr. Thompson seems quite willing to assist in the renovation. It's the great thing about actors: they're malleable molds into which one can pour the character one wishes to see.