Sen. Mitch McConnell, the chief opponent of campaign spending limits and the likely lead plaintiff in the case, announced his legal team Thursday. A day earlier, the Senate passed and sent to President Bush the most extensive changes in campaign finance law in a quarter-century.
Starr, who investigated the Whitewater and Monica Lewinsky cases that led to the impeachment of President Clinton, will be joined by Floyd Abrams, a well-known First Amendment lawyer, and Kathleen Sullivan, dean of the Stanford Law School.
"These are perilous waters into which the Republic has now sailed," Starr said at a news conference with McConnell, R-Ky.
"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."
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.
Sen. John McCain, R-Ariz., the chief sponsor of the legislation with Sen. Russ Feingold, said he was confident the bill "will stand on its merits."
Feingold, D-Wis., said supporters would assemble a legal team, but that the Justice Department would have the primary responsibility for defending the measure once it becomes law.
Mr. Bush has said the legislation is flawed but that he would sign it.
McConnell and other opponents contend that large portions of the bill violate First Amendment free speech rights by restricting the political spending of individuals and groups.
Their biggest target is a provision that bars the use of unregulated "soft money" in the final 30 days of a primary or 60 days of a general election for the broadcast of "issue ads" that mention a candidate by name, often with the purpose of attacking him.
Supporters say anyone can run issue ads as long as they use highly regulated and limited contributions known as "hard money." Under the legislation, the most an individual can contribute in hard money to a candidate per election would be $2,000, double the current ceiling.
A larger issue is the ban on the hundreds of millions of dollars of "soft money" that the national parties receive from corporations, unions and individuals.
"That issue will be raised in this challenge," Abrams said, adding that it was possible that the court would review the stance it has held in this area since 1976.
In 1976, two years after the last major congressional effort to limit political spending, the high court ruled in Buckley v. Valeo that Congress could set limits on political contributions but that limits on spending violated free speech rights.
The campaign finance bill, sponsored in the House by Reps. Christopher Shays, R-Conn., and Martin Meehan, D-Mass., would go into effect on Nov. 6, the day after this year's congressional elections.
McConnell said that his legal team would also include James Bopp, general counsel for the James Madison Center for Free Speech; Bobby Burchfield, an election lawyer who was involved in the Buckley v. Valeo case, and Washington election lawyer Jan Baran.
He said other corporations, unions and interest groups that oppose the bill are also expected to join him as plaintiffs.