As they struggle over whether to filibuster the judicial nomination of Miguel Estrada, Senate Democrats face another question with broader implications: how far they are willing to go in trying to block some of the most conservative aspects of President Bush's agenda.

Late last week, a substantial majority of Democratic senators appeared to be opposed to the appointment of conservative 42-year-old lawyer to the U.S. Court of Appeals for the District of Columbia Circuit; they questioned his experience and accused Estrada and the administration of withholding relevant information about his views.

But they were divided over whether to take the rare if not unprecedented step of trying to kill an appellate court nomination by filibuster, or talking indefinitely to block a vote, and it was not clear whether Estrada foes will have enough votes to do that.

Some wanted to draw a line in the sand to stop the Bush administration from treating them like "rubber stamps." Others worried that they would look as though they were blocking Bush's choices for the bench -- and a Hispanic choice at that -- for political and ideological reasons.

With all 51 Republicans and at least three Democrats supporting him, Estrada would clearly win a simple majority vote. But 60 votes are needed to break a filibuster, and Democrats would need 41 of their 49-member caucus to keep it going -- which one Democratic leader said is possible but not likely.

Politically at least, there are risks regardless of which course the Democrats take.

If they back off a fight that they have elevated to an important test of constitutional rights and duties, they are liable to be accused by liberal loyalists, part of their core constituency, of political cowardice.

If they block Estrada, they will almost certainly be accused by Republicans of "obstructionism" in an echo of charges raised in last year's campaign, which resulted in the GOP takeover of the Senate. Republicans, eager to renew the charge, accused Democrats of threatening a filibuster before they even took up the question.

"It's always politically risky when you stick your neck out . . . but failure to act has consequences as well," said Sen. Richard J. Durbin (D-Ill.), who voted against Estrada's nomination as a member of the Judiciary Committee and advocates a filibuster now that the nomination is before the Senate.

The question "gives people a nervous stomach," said Sen. John Breaux (La.), one of three Democratic senators who support Estrada and oppose a filibuster. "The filibuster is the only weapon we have, and it's got to involve something people understand . . . not just lawyer-speak," he added.

Filibusters and threats of filibusters have become commonplace in the Senate, and both parties have used delaying tactics to slow action on judges. But a review by the Congressional Research Service turned up no cases of a judicial nomination being blocked by a filibuster since President Lyndon Johnson's nomination of Abe Fortas as chief justice was withdrawn in the face of a failed attempt to force a vote in 1968.

This history is troubling to some senators. Others, although bothered by the absence of information about the kind of judge that Estrada would be, question whether this is enough to justify rejection. Still others worry that Republicans will try to use their opposition to the first Hispanic named to the D.C. appeals court -- and a possible Supreme Court nominee -- to undermine support for Democrats in the Hispanic community.

For some, it is also a question of priorities: how many Bush initiatives they can oppose without being tagged as obstructionists, a label that stuck last year after Democrats delayed passage of legislation creating the Department of Homeland Security because of concern over work rules and collective bargaining rights. Bush will "run against the do-nothing Democrats," a senator said. "It really doesn't matter what we do; they'll charge us with it anyway," another said.

Another factor is the high bar set by Minority Leader Thomas A. Daschle (D-S.D.) and others in deciding whether to filibuster. The question is not how they would line up on the first vote to continue or end the filibuster, but rather "where will you be after two weeks, after the fifth or sixth vote," as one senator put it. That "gave people a lot to think about," another said.

A majority of Democratic senators is opposed to the appointment of Miguel Estrada to the appeals court.