Willis supported United States President Lyndon B. Johnson and Vice President Hubert Humphrey in the 1964 and 1968 campaigns. He compiled a generally liberal voting record in Congress according to Louisiana standards, similar to those of Hale Boggs of New Orleans and James H. Morrison of Hammond. Willis' record was in sharp contrast to the conservative records of longtime colleagues Otto E. Passman of Monroe and Joe D. Waggonner of Plain Dealing, and those later compiled by Speedy O. Long of Jena and John R. Rarick of St. Francisville. But Willis was not nearly as liberal as Gillis Long of Alexandria, who represented the eighth district from 1963 to 1965 and again from 1973 until his death in January 1985.