J.P. Morgan Chase shareholders Tuesday rejected a proposal to split the chairman and chief executive roles, handing bank chief Jamie Dimon a big victory. The shareholder proposal to split his two roles won just 32.2 percent of votes cast, according to preliminary results released at the bank's annual meeting in Tampa, Florida. Shareholders at the nation's largest bank by revenues also reelected the entire J.P. Morgan board, although some board members won by slim majorities.