The group, Public Advocate of the United States, is one of the first conservative organizations to announce anything but support for the judge
Eugene Delgaudio, the president of the group, said in an interview that he hopes his stance will prod others.
"I know that others feel the same way. I know they believe as I do. They're just not going to act," the 50-year-old Northern Virginia man said. "But once I've done it, then they can't claim that no one's opposing Roberts."
"We can't take our limited resources and put it toward a candidate who is not a strict constructionist when we were told he is," Delgaudio said.
The stance by his group, which describes itself as a pro-family organization, puts it in opposition to conservative groups that have endorsed Roberts. A number of liberal groups already oppose President Bush's high court nominee.
Roberts met Tuesday with one senator who is undecided on his nomination, Oregon Democrat Ron Wyden, who said the nominee "would not look favorably" on Congress acting to intervene in an end-of-life case like Terri Schiavo.
Wyden said Roberts told him during their hourlong meeting that Congress can prescribe standards, "but when Congress starts to act like a court and prescribe particular remedies in particular cases, Congress has overstepped its bounds," Wyden said.
Congress pushed through unprecedented emergency legislation aimed at prolonging Schiavo's life by allowing the case to be reviewed by federal courts. The courts rejected that effort.
Delgaudio said his group had planned to send out more than 1 million pieces of direct mail for Roberts, as well as work telephones, poll and conduct petition drives.
But now, "canceling our mail campaign is the least we can do," he said. He said he would poll his group to see if members want him to be neutral, spend money to oppose Roberts or reinstate support.
This is not the first time Delgaudio has gone up against the Bush administration. He criticized Vice President Dick Cheney last year after the vice president, when asked about gay marriage, said, "Freedom means freedom for everyone."
Delgaudio said then: "'Freedom' is not embracing perversion."
The Colorado gay rights case involved Amendment 2, a constitutional amendment approved by voters in 1992 that would have barred laws, ordinances or regulations protecting gays from discrimination by landlords, employers or public agencies such as school districts.
Gay rights groups sued and the U.S. Supreme Court declared the measure unconstitutional in a 6-3 ruling in 1996.
Roberts' role in the case included helping develop a strategy and firing tough questions during a mock court session at Jean Dubofsky, a former Colorado Supreme Court justice who argued the case on behalf of the gay rights plaintiffs.
Arguments that Roberts' work on the case does not equal support for gay rights doesn't wash with Delgaudio.
"Nobody's forced to help your opponents," he said. "I can't believe that a senior attorney would voluntarily help somebody he doesn't agree with. I don't believe it. It's not credible."
Other conservative groups, including the Traditional Values Coalition and Focus on the Family Action, the political arm of the Colorado Springs-based conservative Christian ministry Focus on the Family, are still supporting Roberts.
"We support President Bush and his choice for the Supreme Court, John Roberts," said the Rev. Lou Sheldon, founder of the Traditional Values Coalition.
Other groups also are taking public stands on Roberts' candidacy.
NARAL Pro Choice America plans to start running television ads opposing Roberts on Wednesday, and other abortion rights groups including the National Organization for Women, the National Abortion Federation and the Feminist Majority all have announced their opposition to Roberts.
The conservative Progress for America is launching a counteroffensive against NARAL's ads, spending $300,000 for one week's worth of ads on broadcast television in Maine and Rhode Island and on national cable television networks. The ads criticize NARAL's ads, calling them "a desperate and false attack — recklessly distorting Judge Roberts' record."
The National Association of Manufacturers, led by Republican John Engler, is expected to announce an endorsement of Roberts on Wednesday.