Political scientist Charles Murray has never backed away from controversy, but usually his opponents have been liberals. Friday, however, he managed to upset conservatives at the annual conference known as CPAC, where thousands of bewildered Republicans gathered to figure out the way forward after their party’s 2012 electoral defeat. Murray ditched his prepared remarks on “America Coming Apart” in favor of an impromptu admonition to fellow conservatives to accept the legalization of both gay marriage and abortion.

Murray, who is currently a fellow at the American Enterprise Institute, is revered by many conservatives. (He considers himself a libertarian.) His 1984 book “Losing Ground,” which blamed social programs for worsening poverty, and his 1994 book, “The Bell Curve,” which ascribed lower I.Q. scores to some minorities, have been attacked by liberals but embraced as game-changers by many conservatives.

As he got warmed up, Murray explained that, while driving for more than an hour that morning to the conference, he had begun talking out loud to himself, which is how he usually practices his speeches. Upon realizing that he had more than an hour’s worth of fresh thoughts, he decided to simply drop the planned ones. The question on his mind was “How can conservatives make their case after the election?,” and the answer he wanted to share was drawn from his experience with his own four children. They range in age, he said, from twenty-three to forty-three. While they share many of his views on limiting the size of government, and supporting free enterprise, he said, “Not one of them thought of voting for a Republican President” in the last election. Their disenchantment with the Republican Party was not specifically because of Mitt Romney, he added, but because, “They consider the Party to be run by anti-abortion, anti-gay, religious nuts.”

“With gay marriage,” he went on, “I think the train has left the station.”

Certainly the locomotive power of the issue seemed hard to miss on a day when the top political news was Ohio Republican Senator Rob Portman’s announcement that he, too, supports gay marriage. (Richard Socarides has more on that.) While Portman’s position shifted because of his family situation—he explained publicly for the first time that his son had come out as gay—Murray said his own views had been influenced heavily by friends. “I was dead-set against gay marriage when it was first broached,” Murray said; as a fan of Edmund Burke, he regarded marriage as an ancient and indispensable cultural institution that “we shouldn’t mess with.” He used to agree with his friend Irving Kristol, the late father of neo-conservatism, that gay people wouldn’t like marriage. “ ‘Let them have it,’ ” he recounted Kristol as saying, with a chuckle. “ ‘They wont like it.’ ” Murray said that he himself used to think that “All they want is the wedding, and the party, and the honeymoon—but not this long thing we call marriage.”

But since then, Murray said, “we have acquired a number of gay and lesbian friends,” and to what he jokingly called his “dismay” as a “confident” social scientist, he learned he’d been wrong. He’d been especially influenced by the pro-gay-marriage arguments made by Jonathan Rausch, an openly gay writer for the National Journal and the Atlantic. Further, Murray said, he had discovered that the gay couples he knew with children were not just responsible parents; they were “excruciatingly responsible parents.”

By this time, the CPAC audience’s rustlings had an anxious edge. Murray’s remarks seemed to surprise many in the conference room at the National Harbor Convention Center, south of Washington, even if, when it comes to gay marriage, they shouldn’t have: he’s talked about the change in his personal views before, as David Weigel and Andrew Sullivan have noted. What was striking was how critical he argued it is for the G.O.P. to make a similar shift as a party.

The disquiet grew further as Murray suggested that abortion, too, was an issue better left, for the most part, to “moral suasion” rather than criminalization. Personally, he said, he regarded abortion as a “grave” moral issue, and favored some restrictions. He said he’d like to see Roe v. Wade overturned, and abortions regulated at the state level. But, he said, “the extent to which they can be legislated remains in question.” Rather than absolutely banning abortion, as many conservatives in the room clearly preferred, Murray quoted his friend Karl Hess, a Goldwater speechwriter turned “charming anarchist,” on the idea that abortions should be thought of as homicides—with the caveat that, “It’s a murder—it’s a homicide—but sometimes homicide is justified.” Murray said that he’d long thought that Hess was too harsh, but now thought that his language was right.

Unless the G.O.P. drops what he called its “litmus tests” for candidates on these divisive social issues, Murray warned that conservatives were likely to alienate a large swath of the voting public, including his children, who might otherwise be attracted to the Party. He admitted, though, that, “I’m not known as an astute electoral analyst.”

This admission seemed born out by the dynamic in the conference room. Although there was some praise for Murray during a question period following his talk, several members of the audience pointedly shook their heads, and at least one young man stood up and walked out, illustrating the G.O.P.’s dilemma: it’s hard to move forward without simultaneously running the risk of, as Murray might put it, losing ground.