Senate Democrats are pressing for extensive records on the participation of Judge Samuel Alito in an appeals case involving a mutual fund company with which he had a six-figure investment.

In their first coordinated challenge to Alito's nomination to the Supreme Court, the eight Democrats on the Senate Judiciary Committee on Wednesday sent a letter to the 3rd U.S. Circuit Court of Appeals saying Alito had promised the panel in 1990 he would "disqualify myself from any cases involving the Vanguard companies."

The letter requests the original opinion in the 2002 case, which was unpublished. It also seeks any communication "from or to the White House, the Justice Department ... or anyone else on their behalf" concerning Alito's decision to participate in the case, in which a three-judge panel ruled on behalf of Vanguard and other investment firms. The companies had been sued by a widow who claimed she was denied funds originally belonging to her deceased husband.

The White House, saying Alito has acted ethically throughout his career, dismissed the suggestion that there was something wrong in this case. "Judge Alito looks forward to answering any questions that committee members may ask him at the hearing about this issue," said Steven Schmidt, an administration spokesman.

Apart from the written requests, several Democrats who have met privately with Alito in recent days told reporters they had raised conflict-of-issue concerns. "I asked him a lot of questions about Vanguard and there are going to be more," said Sen. Russell Feingold, D-Wis.

The letter comes at a time when Alito appears to be gaining ground steadily in his confirmation campaign for the seat held by Justice Sandra Day O'Connor, with Democratic critics struggling to slow his momentum.

Conservative senators whose silence helped torpedo Harriet Miers' appointment earlier this fall have rallied to Alito's side. Some Democrats have said they do not expect a filibuster — angering others in the party who want to preserve their right to try and deny Alito a yes-or-no vote when his nomination reaches the full Senate.

Additionally, several lawmakers of both parties who helped defuse a showdown over Bush's conservative appeals court nominees last spring have signaled they will be unsympathetic to a filibuster should liberal opponents seek to prevent a final vote.

Democrats from Republican-leaning states have praised Alito without endorsing him. "I found him to be very impressive, I found him to be a very thoughtful person," said Sen. Kent Conrad, D-N.D. "... Absolutely he is conservative, but I believe in the broad mainstream of American jurisprudence," he added.

The Judiciary Committee has scheduled hearings for Alito beginning Jan. 9, and Sen. Arlen Specter, R-Pa., the panel's chairman, has said he hopes for a final vote by the full Senate on Jan. 20. That would come two days before the anniversary of the 1973 ruling that established abortion rights — Roe v. Wade — the decision many conservatives hope Alito will overturn if confirmed for the seat held by O'Connor.

O'Connor's vote has been pivotal on the court on abortion, affirmative action and other issues, and partisans on both ends of the political spectrum say that elevates the importance of Alito's nomination.

Alito reported holdings of about $80,000 in Vanguard funds when he was confirmed in 1990 to the appeals court seat, and news articles around the time of the disputed case placed his investment at $390,000 or above.

Schmidt, the White House spokesman, pointed to letters by two law professors who wrote Specter earlier this month, saying Alito had handled the 2002 case properly.

At the same time, the Republican National Committee circulated material criticizing Sen. Edward M. Kennedy for challenging Alito's behavior in the 2002 case — then praised the Massachusetts Democrat for defending Justice Stephen Breyer against conflict-of-interest allegations at his 1994 confirmation hearings.

Kennedy wrote Alito on Tuesday, posing a series of questions about the case and noting his 1990 pledge to the Judiciary Committee.

The letter by the committee's eight Democrats, addressed to Anthony J. Scirica, chief judge of the 3rd U.S. circuit court of appeals, escalated the issue.

Based on Kennedy's letter as well as the one issued to the appeals court, there seems to be little controversy about the ruling in the Vanguard-related case, in which the Supreme Court declined to hear an appeal from the decision made by Alito and two other appeals court judges.

Instead, the Democrats turned their attention to the 1990 pledge to the Judiciary Committee and his decision not to disqualify himself.

In the 2002 case, Shantee Maharaj sought a rehearing after learning Alito held investments in Vanguard, and she sought to erase the ruling and disqualify him from further proceedings.

Alito wrote a letter to the chief judge saying he did not believe he was required to disqualify himself on the basis of ownership of shares in a mutual fund. At the same time, he was voluntarily recusing himself from a decision on whether to wipe out the original ruling. He did not mention the pledge he had made to the Senate.