In 1952, he and a partner named Weldon Weekley founded Weekley & Valenti, an advertising agency, with oil company, Conoco, as its first client. In 1956, Valenti met then Senate Majority Leader Lyndon B. Johnson. Weekley & Valenti branched out into political consulting and added Representative Albert Thomas, a Johnson ally, as a client. In 1960, Valenti's firm assisted in the Kennedy-Johnson presidential campaign.