Washington ? Senate Republicans set the stage for a showdown Tuesday over the filibusters blocking several of President Bush’s judicial nominees, a historic vote that could determine whether an out-of-power party can stop a president from placing like-minded jurists on the nation’s highest courts.

Unless compromise-minded centrists can strike a deal before then, Senate Majority Leader Bill Frist will force a test vote Tuesday on Texas judge Priscilla Owen’s nomination to the 5th U.S. Circuit Court of Appeals.

Under the expected chain of events set in motion Friday: If the nomination doesn’t garner 60 votes – the threshold for overcoming a filibuster – Frist then will have the presiding officer, expected to be Vice President Dick Cheney in his role as Senate president, declare that filibusters are illegal for Supreme Court and federal appellate court nominees.

The Republican majority presumably then would uphold that ruling.

“The Senate clock centered above the vice president’s chair is in a countdown, second by second, to the appointed hour and minute when a nuclear explosion may render the Senate inoperative, or at least do substantial damage to this institution,” said Judiciary Chairman Arlen Specter, R-Pa.

GOP Sen. John Cornyn, a former judge who served with Owen on the Texas Supreme Court, started the countdown Friday by demanding a vote on her nomination. When Democratic leader Harry Reid blocked that vote, Cornyn called for the Tuesday test vote.