WASHINGTON — To forgive is divine. To forget may be asking too much of religious conservatives when it comes to Senator McCain. The Republican presidential hopeful is working hard to repair relations with conservative Christian activists, whose support could be critical to winning the GOP nomination. But they remain skeptical that he sincerely shares their values.

While Mr. McCain has managed to pry open some of the doors that slammed shut in his rift with the right during his bid for the presidency in 2000, conservatives’ list of grievances against the Arizona senator is substantial:

• They are dubious about his opposition to a federal amendment to ban gay marriage. Mr. McCain opposes same-sex marriage, but he says it should be regulated by the states.

• They still resent passages in the McCain-Feingold campaign finance law, which Christian broadcasters say limit what they can tell voters before elections.

• And they question the sincerity of his overtures. Mr. McCain condemned evangelist leaders Pat Robertson and Jerry Falwell as “agents of intolerance” during his 2000 run.

Christian leaders still have “a lot of questions” about Mr. McCain, said Paul Weyrich, who founded the Moral Majority with Mr. Falwell and pioneered efforts to mobilize evangelical voters.

McCain-Feingold “is a big stumbling block for all of us,” Mr. Weyrich said. He and others also say Mr. McCain, a four-term Arizona senator, largely ignored a measure on the November ballot to ban gay marriage in his home state, although he did endorse it in a TV ad. Arizona was the only state where the effort failed in the last election.

“It seems to me that if he were really sincere, he would have gone in with both feet and supported that amendment,” Mr. Weyrich said.

Focus on the Family founder James Dobson was more blunt.

“I would not vote for John McCain under any circumstances,” Mr. Dobson said last month on KCBI, a Dallas Christian radio station. “I pray that we won’t get stuck with him.”

Mr. McCain is trying hard to avoid a repeat of the 2000 GOP presidential primaries in which the current president ultimately mobilized Christian conservative activists to sink Mr. McCain’s campaign. Prominent Christian leaders, including Messrs. Robertson and Falwell, opposed Mr. McCain in 2000, partly because they didn’t feel he was conservative enough on their issues. “We’ve continued to reach out to leaders in these very important states and communicate the senator’s record of advocacy for conservative causes,” said Danny Diaz, a spokesman for the McCain campaign. “What we’ve seen is a strong response and support.”

Contributing to Mr. McCain’s strained relations with religious conservatives was his past criticism of the fundamentalist Christian college Bob Jones University in Greenville, S.C., for its ban on interracial dating. Political activists associated with the university helped defeat Mr. McCain in the 2000 South Carolina primary.

The school has since lifted the ban. Mr. McCain now says he wouldn’t turn down an opportunity to speak there.

He also has hired David Rexrode, a veteran campaigner who organized evangelical voters for the Bush-Cheney campaign in 2004, to help repair the damage.

Mr. McCain has made amends with Mr. Falwell. He spoke at Mr. Falwell’s Liberty University last spring. On Monday, Mr. Falwell and five other religious leaders will host a “meet and greet” for Mr. McCain at the National Religious Broadcasters Convention in Orlando, Fla. — a big step, although Mr. Falwell has been careful to say it does not constitute an endorsement.

But other efforts aren’t going as smoothly.

Mr. McCain has said he hopes to patch things up with Mr. Dobson, but Mr. Diaz wouldn’t say whether Messrs. Dobson and McCain have spoken. Mr. Dobson declined a request for an interview and a Focus on the Family spokesman said Mr. Dobson had nothing more to say about Mr. McCain.

Mr. Robertson also declined to discuss Mr. McCain.

Mr. McCain’s seeming about-face with the Christian right also has drawn criticism from Democrats and eroded his image that appealed to swing voters in 2000.

In Mr. McCain’s home state, Rep. Trent Franks — a staunch opponent of abortion and gay marriage — has split with the rest of the Republicans in the Arizona congressional delegation, refusing to back the senator’s presidential bid. Instead, he’s supporting a long-shot GOP candidate, Rep. Duncan Hunter of California, whom he calls an “unequivocal social and fiscal conservative.”

But Mr. McCain has at least one thing going for him with the religious right: Christian leaders are also wary of the other leading GOP presidential hopefuls, a former Massachusetts governor, Mitt Romney, and Mayor Giuliani.

Mr. Giuliani supports abortion rights and gay rights. Mr. Romney has supported both in the past, although he now opposes abortion and gay marriage.

With no clear social conservative among the top-tier candidates, religious right leaders like the Iowa Christian Alliance’s Steve Scheffler say they are now at least willing to give Mr. McCain a chance to explain himself.

That’s a turnabout from last April, when Mr. Scheffler told the Associated Press, “There’s no support for McCain in this constituency.”