The Federal Bureau of Investigation said it was looking into allegations by Senator Mitch McConnell of Kentucky that political opponents bugged his campaign headquarters.
Mr. McConnell, the Republican leader in the Senate, blamed the “political left” for an anonymous recording of a meeting at his campaign headquarters that appeared on the Web site of Mother Jones, a liberal magazine, on Tuesday morning. The recording captures Mr. McConnell and his aides outlining possible attacks on potential opponents, especially the actress Ashley Judd.