Along with California Senator Barbara Boxer, Harkin was one of only two Senate Democrats to come out in favor of Wisconsin Senator Russ Feingold's resolution to censure President George W. Bush.
Harkin (in addition to U.S. Senators Dick Lugar, Tim Johnson, Byron Dorgan, Joe Biden and Barack Obama), introduced the BioFuels Security Act (S. 2817/109th) on March 16, 2006.