WASHINGTON (Reuters) - Lawmakers charged with enforcing ethics in the U.S. House of Representatives met on Thursday to begin an investigation of a sex scandal that has ensnared top Republicans and could harm their chances of keeping control of Congress in the November 7 elections. The top Republican in the House, Speaker Dennis Hastert, also scrambled to keep his job amid criticism of how he handled the case of former Republican Rep. Mark Foley (news, bio, voting record)'s unwanted advances on teenage boys. Foley resigned last week after disclosure of his lurid electronic messages. With polls beginning to show the...