Washington ? Kenneth Starr, the former Whitewater independent counsel, will lead the court challenge seeking to overturn large parts of the campaign finance bill passed by Congress.

Sen. Mitch McConnell, expected to be the lead plaintiff in the case, said Thursday that his legal team would be led by Starr, who gained national prominence in his pursuit of former President Clinton over the Whitewater land deal and the Monica Lewinsky case, and by First Amendment lawyer Floyd Abrams.

“This is a mission to preserve the fundamental constitutional freedom of all Americans to fully participate in our democracy,” said McConnell, R-Ky.

The Senate on Wednesday passed and sent to President Bush the most far-reaching campaign finance legislation in the past quarter-century. It bans the hundreds of millions of dollars in unregulated “soft money” that corporations, unions and individuals give the national political parties and restricts in the final days before an election the use of soft money for “issue ads” that name a candidate, often with the purpose of attacking him.

Bush said the bill is “flawed,” but promised to sign it because he said it improves the system overall.

McConnell said opponents plan to file their lawsuit before a three-judge panel in U.S. District Court in Washington, D.C., with the expectation that it would move quickly to the Supreme Court.

“These are perilous waters into which the Republic has now sailed,” Starr said at a news conference with McConnell. “The questions are grave, the questions are serious. It is now time for the courts to speak authoritatively to what the Congress has chosen to do.”

Sen. Russ Feingold, D-Wis., who sponsored the campaign finance bill in the Senate with Sen. John McCain, R-Ariz., said he believed the measure protected First Amendment rights. He said they will assemble their own legal team, and he has Atty. Gen. John Ashcroft’s assurance that the Justice Department would defend the statute’s constitutionality.

The legality of campaign finance legislation has been an issue since the last effort to limit campaign spending in 1974. In 1976, in Buckley v. Valeo, the Supreme Court ruled that Congress could set limits on contributions, but that limits on spending violated free speech rights.

McConnell and his team said they would focus on a provision that bars the use of soft money 30 days before a primary or 60 days before a general election for “issue ads” that refer directly to a candidate.

Supporters of the bill say anyone can run issue ads as long as they use highly regulated and limited contributions of “hard money.” Under the legislation, the most that an individual can contribute in hard money to a candidate would be $2,000, double the current ceiling.