Representative Steven C. LaTourette, a nine-term lawmaker and a confidant of House Speaker John A. Boehner, has decided not to run again. Ohio Republican Party Chairman Bob Bennett said Monday night that Mr. LaTourette had told him that he would not run in November. He would not comment on Mr. LaTourette’s reasons for retiring. But The Columbus Dispatch, which first reported the decision, said that Mr. LaTourette decided to retire over a dispute with the leadership on committee assignments.