Supreme Court nominee Clarence Thomas moved a step closer to confirmation yesterday as two more Democratic senators announced their support and the Senate agreed to vote on the nomination next Tuesday.

Thomas appeared assured of at least 51 votes when Sens. Richard C. Shelby (D-Ala.) and Alan J. Dixon (D-Ill.) endorsed him, bringing to 11 the number of Democrats who have said they will vote for the nominee.

In a speech to the Senate, Shelby said Thomas would bring a "unique perspective" to the high court because of his rise out of poverty under the "worst of Jim Crow segregation laws" in rural Georgia.

Dixon later issued a statement that also spoke admiringly of Thomas's background. "The hardscrabble beginnings in Pin Point, Ga., his successful struggle out of poverty and the incidents of racism directed at his family and him have constructed a most unique background for someone to be on the Supreme Court," Dixon said.

The Shelby and Dixon statements were made as the Senate spent the day trying to disentangle itself from a partisan flap over parental leave legislation that threatened to delay action on Thomas.

After nine hours of haggling, senators last night resolved the dispute over voting on the leave bill, which would guarantee workers up to 12 weeks of unpaid leave annually to care for newborn children or ill family members, and scheduled it for a vote today. They also agreed to begin debate on Thomas Thursday and vote on the nomination at 6 p.m. Tuesday.

This means the Senate will delay the start of its week-long Columbus Day recess that was due to start Friday. But, if Thomas is confirmed, he would be able to join the court on Wednesday. The court begins its fall term Monday.

When Republicans objected to a recorded vote on bringing up the leave bill, Democrats warned that GOP delaying tactics could force a delay on Thomas. The administration and Senate Republicans had been pressing for a prompt vote on Thomas.

In endorsing Thomas, Shelby split with his senior senator, Howell Heflin (D-Ala.), whose vote against Thomas in the Senate Judiciary Committee contributed to the panel's 7 to 7 tally on the nomination last month. As a result of the split, the committee sent the nomination to the floor without recommendation.

"There is no doubt in my mind that Judge Thomas' life and work experiences would serve him well on the Supreme Court," Shelby said. "I especially believe that Judge Thomas brings a unique perspective -- that of a minority in America -- that would better enable the Supreme Court to ensure that the rights and freedoms of all Americans are preserved and strengthened."

Shelby, who was elected to the Senate with strong support from blacks in Alabama and is up for reelection next year, joins nine other moderate-to-conservative Democrats planning to vote for Thomas: J. Bennett Johnston (La.), John B. Breaux (La.), Sam Nunn (Ga.), Ernest F. Hollings (S.C.), J. James Exon (Neb.), Richard H. Bryan (Nev.), Harry Reid (Nev.), Dennis DeConcini (Ariz.), and David L. Boren (Okla.).

Among Democrats who have not announced a position on Thomas are several who are regarded as possible or even likely supporters, including Bob Graham (Fla.).

No Republicans have announced opposition to Thomas. Sens. William S. Cohen (R-Maine) and James M. Jeffords (R-Vt.) are considered the most likely swing votes.

Meanwhile yesterday, Thurgood Marshall, the justice Thomas would replace, formally retired and ended speculation about whether he would sit at the start of the Supreme Court term next Monday.

Marshall's initial letter of retirement indicated his intention to step down "when my successor is qualified." In a letter delivered to President Bush yesterday, Marshall said, "I now request that my retirement become effective as of this date."

Marshall, who had heart surgery this summer, did not provide a reason for his decision.

As Democrats were seeking to use Thomas's nomination as leverage to force action on the parental leave bill, the judge's wife, Virginia Lamp Thomas, who is deputy assistant secretary of labor for congressional affairs, was working the Senate corridors on behalf of the administration position against the leave bill.

Sen. Patrick J. Leahy (D-Vt.) said he had no quarrel with her lobbying efforts but added that some senators who were supporting the leave bill as well as Thomas's nomination were "grinding their teeth" over what they regarded as an unwelcome appearance of linkage between the two matters.

Staff writer Ruth Marcus contributed to this report.