The "Obamacans" that Sen. Barack Obama used to joke about - Republican apostates who whispered their support for his candidacy - have morphed into a new phenomenon, or syndrome, as detractors like to call it: the Obamacons.

These are conservatives who have publicly endorsed the presumptive Democratic nominee, dissidents from the brain trust of think tanks, ex-officials and policy magazines that have fueled the Republican Party since the 1960s. Scratch the surface of this elite, and one finds a profound dismay that is far more damaging to the GOP than the usual 10 percent of registered Republicans expected to switch sides during a presidential election.

"The untold story of the Bush administration is the deliberate annihilation of the Reaganite, small-government wing of the Republican Party," said Michael Greve, director of the Federalism Project at the American Enterprise Institute, a conservative think tank. "A lot of people are very bitter about it."

Many conservatives and their brethren, the free-market, socially liberal libertarians, are deeply skeptical of Obama's rhetorical flirtations with free-market ideas and view his policies as orthodox liberalism. Yet one measure of their rupture with the GOP is their open disregard for Republican nominee John McCain and their now almost-wistful view of a president the Republicans tried to impeach.

"When he leaves the room, everybody thinks he just agreed with them," Greve said of Obama. "We don't know if you're really buying a pig in a poke here. It could be the second coming of the Clinton administration. If people have any confidence in that, I think a whole lot of conservatives would vote for him."

Such sentiments reflect a collapse of the "big tent" conservative coalition that Republican President Ronald Reagan forged in 1980, uniting free-market, small-government types, Christian evangelicals, cultural traditionalists and anti-communists, now called neoconservatives. The neoconservatives, whose intellectual leaders include New York Times columnist David Brooks and Weekly Standard publisher Bill Kristol, remain firmly inside the GOP and strongly back McCain, who appeals to their model of "national greatness." So do mainstream conservative think tanks such as the Heritage Foundation, which issues regular attacks against Obama's economic plans, and the traditionalist magazine National Review.

The left often lumps these factions together, but the Iraq war and President Bush's "compassionate conservatism" that led to an expansion of government have ruptured the coalition. Many conservatives are aghast at the rise in spending and debt under the Bush administration, its expansion of executive power, and what they see as a trampling of civil liberties and a taste for empire.

"I do know libertarians who think Obama is the Antichrist, that he's farther left than John Kerry, much farther left than Bill Clinton, and you'd clearly have to be insane to vote for this guy," said David Boaz, executive vice president of the Cato Institute, a libertarian think tank. "But there are libertarians who say, 'Oh yeah? Do you think Obama will increase spending by $1 trillion, because that's what Republicans did over the past two presidential terms. So really, how much worse can he be?' And there are certainly libertarians who think Obama will be better on the war and on foreign policy, on executive power and on surveillance than McCain."

Libertarians are tired of Christian evangelicals, who they believe captured the GOP under President Bush. Evangelicals, for their part, are skeptical of McCain, who in 2000 called Jerry Falwell and Pat Robertson "agents of intolerance." McCain has tried to make amends, promising to stand firm on abortion and same-sex marriage, and appoint conservative Supreme Court justices, but mistrust runs deep.

Douglas Kmiec is former chief of the Office of Legal Counsel in the Reagan and George H.W. Bush administrations, and now a constitutional law professor at Pepperdine University and a devout Catholic. Kmiec endorsed Obama earlier this year, despite his conviction that Obama "believes in a pretty progressive agenda."

Kmiec said his support deepened after meeting with Obama and other faith leaders last month, during which the busy candidate spent 2 1/2 in a freewheeling discussion with people who differed with him.

"I think he's the right person at the right time to re-establish principles of constitutional governance that have been ill treated by the current administration, and to free us from the tar paper that we know is Iraq," Kmiec said, adding that many Republicans privately agree. "I think he's a man in the market for every good idea he can find, and he doesn't care what label it comes with."

David Friedman, the son of late conservative icon and Nobel economist Milton Friedman, has also endorsed Obama. Calling McCain a "nationalist," Friedman, an economist at Santa Clara University, thinks Obama could turn out like the liberals who deregulated New Zealand's economy.

"Of the two, Obama is less bad and at least has a chance in some ways of being good," said Friedman. Friedman likes Obama's University of Chicago advisers such as Austan Goolsbee and Cass Sunstein, who he believes are trying to forge a new leftism that incorporates free-market views. "I don't expect to agree in general with them," Friedman said, "but I certainly would be happy if the left became more libertarian, since the right seems to be less libertarian than it used to be."

Many see the Iraq war as hostile to conservative values and as a "friend of the state" - something that inherently expands the reach of the government, as Milton Friedman once described war.

"People don't understand that there has always been a small but very significant element of conservatives who have been against the war from day one and who, like me, also hate George Bush and think he's the most incompetent president in American history," said Bruce Bartlett, a supply-side economist who coined the term Obamacons. "The few people who are slavishly pro-Republican, live or die, slavishly pro-Bush like the Weekly Standard crowd, have gotten lot more publicity than they deserve."

Many conservatives are looking for a Clintonesque "Sister Soulja" or "end welfare as we know it" moment from Obama, a concrete demonstration of a willingness to abandon Democratic dogma.

"The Republicans have left the libertarian baby on the doorstep, but Democrats won't open the door," said Boaz. "There are people saying Obama's a University of Chicago Democrat, and you can't spend 10 years at the University of Chicago without having some appreciation for markets. I'd like to believe that. I just don't see the rubber meeting the road."

Matt Welch, editor in chief of the libertarian Reason Magazine and author of "McCain, the Myth of a Maverick," thinks Obama's conservative support "comes as much anything else from people being exhausted with the Republican coalition, who are mad at one wing or another, and they just think it's time for them to lose. It's just, 'Look, we're out of ideas, we're exhausted, it's not working, we don't know what our principles are anymore, let's take one for the team and have a black guy be the president for a while.' "

Obama is actively trying to switch one prominent Republican to an Obamacan: former Secretary of State Colin Powell, who met with both candidates last month.