WASHINGTON – Republicans and Democrats injected racial politics into the struggle over President Bush’s judicial nominees and the Senate’s filibuster rules yesterday, underscoring partisan differences while centrists of both parties pursued an elusive compromise.

“The attempt to do away with the filibuster is nothing short of clearing the trees for the confirmation of an unacceptable nominee to the Supreme Court,” said Democratic Leader Reid. He accused the president of an attempt to “rewrite the Constitution and reinvent reality” with his demand for a yes-or-no vote on all nominees.

Democrats are guilty of “unprecedented obstruction,” countered Republican Whip McConnell of Kentucky, arguing that Mr. Bush’s Senate critics had overturned 214 years of tradition by blocking votes on several of the president’s conservative candidates.

The day of choreographed debate on the floor unfolded as compromise minded senators negotiated privately in the office of Senator McCain, a Republican of Arizona, and leaders of both parties held dueling staged-for-television events designed to court black voters.

“Why are they afraid to put a black woman on the court?” asked Bishop Harry Jackson, chairman of a group of black pastors, standing next to Majority Leader Frist at a news conference outside the Capitol. He called Justice Janice Rogers Brown, a California Supreme Court justice whom Mr. Bush has named to the federal appeals court, “not only a legal hero for black America, she is a legal hero for all America.”

Mr. Frist, a Republican of Tennessee, did not mention Justice Brown’s race in his own remarks. He said Democratic treatment of her nomination was “unnecessary, uncivil. It is injustice. I pledge to you here today that I will do everything in my power to see that it stops.”

He made his comments after members of the Congressional Black Caucus said he had declined to meet with them to discuss the issue. The Democratic lawmakers proceeded to a news conference where they released a letter to the Tennessee Republican arguing that his call for a partial ban on judicial filibusters “would be particularly offensive to people of color.”

There was irony – as members of the caucus noted – since the historic civil rights legislation of a half-century ago was passed only after supporters overcame filibusters by conservative Southern Democrats and likeminded Republicans.

“The filibuster was systematically used when Senate minority rights meant the denial of the rights of African-Americans,” caucus members wrote. “We cannot and will not stand down when Senate minority rights are proposed to be overruled against a Senate minority that seeks to protect the rights of African-Americans.”

Mr. Frist has set the Senate on the path for a showdown next week on his bid to eliminate the Democrats’ ability to filibuster present and future appeals court and Supreme Court nominees. While it takes 60 votes to overcome a filibuster, Republicans intend to supersede the rule by majority vote. With 55 seats, they could afford five defections and still prevail on the strength of Vice President Cheney’s ability to break ties.

Democrats have threatened to slow the Senate’s business to a crawl if Republicans prevail, and they served up a preview during the day when they invoked a rule that prevented some committees from meeting. And with Mr. Frist’s timetable calling for the critical votes to be cast next Tuesday and Wednesday, compromise-minded senators in both parties gathered in Mr. McCain’s office twice during the day.

By agreeing among themselves, any six Republicans and six Democrats would hold the Senate’s balance of power, making it impossible for Mr. Frist to engineer a change in procedures on one hand, and dooming future filibusters on the other.

“We’re making progress but we’re not quite there,” said Senator Pryor, a Democrat of Arkansas, who has been involved in the discussions.

Officials in both parties said there were two stumbling blocks.

One involved which of Mr. Bush’s nominees would be cleared for confirmation and which would continue to be held up. Under discussion when the day began was a plan to allow final votes on Justice Brown as well as Justice Priscilla Owen, named to the 5th Circuit Court of Appeals, and William H. Pryor, a former Alabama attorney general who received a temporary appointment to the 11th Circuit Court of Appeals after Democrats blocked a confirmation vote in Mr. Bush’s first term. The less controversial 6th Circuit Court nominees, Judges Susan Nielson, Richard Griffin and David McKeague, also would be cleared for votes under the proposal.