WASHINGTON — 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.
"They were bugging our headquarters, a quite Nixonian move," Mr. McConnell said at a news conference on Tuesday. "This is what you get from the political left in America these days."
As yet, Mr. McConnell faces no serious challenge to his seat, but the 12-minute tape of a Feb. 2 meeting in Louisville suggests his team was ready, with opposition research gathered by aides to Mr. McConnell's campaign and Senate office.
"This is the Whac-A-Mole period of the campaign," Mr. McConnell said on the tape. "When anybody sticks their head up, do them out."
Ms. Judd's head was up, so to speak, amid speculation that she would run against him in 2014. Along with comments that could mark her as a "carpetbagger" and an "out-of-touch, Hollywood liberal," aides found fodder for less predictable, more personal attacks.
"This sounds extreme, but she is emotionally unbalanced," one man said. He cited her confessions of suicidal tendencies in an autobiography. The group laughed at an interview in which Ms. Judd, in an apparent critique of American consumer culture, said, "I absolutely flipped out when I saw pink fuzzy socks on a rack."
In March, Ms. Judd announced that she would not run for the seat. On Tuesday, Senate Democrats and Ms. Judd's spokeswoman criticized Mr. McConnell for making depression a "laughing matter."
A spokeswoman for the F.B.I.'s Louisville division said the agency was "looking into" the complaints from Mr. McConnell's Senate office.
Mother Jones stood by the report by David Corn, who also published the secret recording of Mitt Romney's "47 percent" comments last year. Without revealing the source, the magazine's statement said, "It is our understanding that the tape was not the product of a Watergate-style bugging operation."
In the tape, McConnell aides acknowledged that they had less material against another potential Democratic challenger, Alison Lundergan Grimes, Kentucky's secretary of state.
On Tuesday afternoon, his campaign invited supporters to "stand with Senator McConnell against illegal wiretapping" by signing up for e-mail or giving a donation.
