Michael Schulman: Fred Thompson's Broadway Debut: The New Yorker If you are a casting director in search of a President, senator, C.I.A. director, district attorney, rear admiral, or other Guy Whose Job Is Really Important, chances are you've put in a call to Fred Dalton Thompson. Thompson, who is seventy-one, has made a career of being both an actual official and an actor who plays one. Before he was the district attorney on "Law & Order," he was a lawyer for the Republicans on the Senate Watergate Committee. Before he was Senator Thompson, of Tennessee, he was Senator Hedges, in the Melanie Griffith film "Born Yesterday." And, before his brief, befuddled run for President, in 2008 (he announced his candidacy on the "Tonight Show"), he was President Ulysses S. Grant, in the TV movie "Bury My Heart at Wounded Knee." "There are very few things that I've played that I haven't either been them or known them," he said the other day. . . .