Oh, plenty. Some did it with men, some with women, but all cheaters:
Mark Foley (mmm, boys), Charlie Christ (mmm, men, but he's getting married again to secure a spot as VP), Gingrich (women, but still a cheater), Ed Schrock (mmm, 1-900- interactive-male), Mayor Jim West of Spokane (again, mmm boys!), Don Sherwood (well they were hot 20 year old women), LaTourette of Ohio (cheated and lobbied with the same girl), Mitch McConnell (remember him?), Bill Frist (an overall scumbag ditching his fiancee the night before they were to be married for a mistress), and Mark Rubio of Miami (men and women, allegedly still).
I am sure there are many more.