"There is a lot of skepticism around about her," Brownback said, recalling the conservative disillusionment with Souter, who ruled in favor of abortion rights and with the majority in other liberal decisions. "If it really appears as if and operates as if she is a Souter type of nominee, I can see a scenario that I would vote against her on the committee."

Another Republican member of the Judiciary Committee, Sen. Orrin G. Hatch of Utah, said Miers had more convincing to do with some of the conservative Republicans than she did with the panel's Democrats.

Still, Hatch, who met with Miers on Tuesday, said he would support her and expected the other Republicans to ultimately do the same. "A lot of my fellow conservatives are concerned, but they don't know her as I do," he said, adding that he would stake his reputation that "she is going to basically do what the president thinks she should, and that is be a strict constructionist."

Staff members of the Senate Republican leadership were already trying to reassure conservative advocacy groups at a meeting on Capitol Hill on Monday night. They brought in Leonard Leo, a conservative lawyer close to the White House and the chairman of Catholic outreach for the Republican Party, to promote Miers' virtues, according to people who attended but did not want to be named because of the confidential nature of the meeting.

But many left unconvinced. "I think what they have given us is a big question mark," said Connie Mackey, the vice president for government affairs of the Family Research Council.

Many social conservatives also reacted with alarm on Tuesday to news reports that as a City Council candidate in Dallas in 1989, Miers told a gay group that she supported equal civil rights for gays and lesbians, although she did not support the repeal of a local ban on sodomy.

Democrats, meanwhile, gave off their own signs of indecision about the nomination. Sen. Harry Reid of Nevada, the Democratic leader, stepped back from the effusive praise of Miers he offered on Monday, saying that even though he had recommended her to the president, he was now reserving judgment.

"Let me make clear that I have not endorsed this nomination," Reid said. "It would be entirely premature of me to do so."

Reid said Miers needed to show that she will rule independently despite her long ties to President Bush. "She needs to demonstrate to the Senate that she can put those close ties aside and, when necessary, stand in judgment of the president who has elevated her to the court," he said.