Sen. Rick Santorum is walking a tightrope this election year as he attempts to appeal to moderates without alienating his conservative base.

On the night before confirmation hearings began in Washington for Supreme Court nominee Samuel Alito, Santorum was alongside Focus on the Family founder James Dobson and the Rev. Jerry Falwell at a Philadelphia rally, voicing support for Alito and accusing liberal judges of "destroying traditional morality."

Just a few weeks earlier, the Pennsylvania Republican canceled his membership in the group that helped defend the Dover School Board in its bid to teach intelligent design, earning him the wrath of at least one conservative group.

Santorum has long been a darling of conservatives for his outspoken opposition to gay marriage. But right now, he's behind in the polls to his likely Democratic challenger, state Treasurer Bob Casey Jr. Pennsylvania went for Democrat John Kerry in the 2004 presidential election and has more registered Democrats than Republicans.

Santorum probably will soften his image with moderates — when he can get away with it with conservatives, said Chris Borick, director of the Muhlenberg College Institute of Public Opinion. For example, Borick noted, Santorum supported an amendment to raise the minimum wage and wrote a letter to President Bush last week asking for creation of a commission that would examine progress in Iraq.

Conservatives will probably forgive him for deciding to withdraw his membership from the board of the Thomas More Law Center, which backed the intelligent design case, Borick said. But they might not if Santorum fails to work publicly toward establishing a conservative majority on the Supreme Court.

"To prove your conservative stripes, being unwavering on putting together a more conservative court is necessary," Borick said.

Diane Gramley, president of the American Family Association of Pennsylvania, which issued a statement criticizing Santorum after he withdrew from the Thomas More board, said Monday she would still probably vote for Santorum in November.

"With any politicians there's going to be bumps in the road and they are not going to do things the way they should," Gramley said. "Unfortunately, that's part of the political scene."

Casey has accused Santorum of flip-flopping, an allegation Santorum denied on Monday.

"I try to do my job. I don't worry about reaching out and holding on," he said before an agriculture field hearing he chaired in Harrisburg, Pa.

Santorum said he withdrew from the Thomas More board because he disagreed with its handling of the case.

Tony Perkins, president of the Family Research Council, which organized Sunday's rally, and Michael Geer, president of the conservative Pennsylvania Family Institute, brushed aside suggestions that Santorum withdrew to appeal to moderate voters.

"He was not, I don't think, speaking about the issue of religious liberty or intelligent design at all, but the specifics of the case and we ... quite frankly agree with him," Geer said.