Liberals have every reason to be pleased with the three remaining Democratic presidential candidates and what they portend for the vitality of political liberalism in the Democratic Party. The same cannot be said for conservatives concerning the Republican candidates and the vitality of conservatism.

There isn't a dime's worth of ideological difference between Hillary Clinton, Barack Obama and John Edwards. They just present their respective brands of statism in different ways. In the Democratic Party, big-government liberalism is alive, well, robust and vibrant.

Hillary might resume "Third Way" Clintonian politics if she wins the nomination, but for now, she's bragging that her health-care plan is more Marxist than Barack's.

But for Republicans, there's a fierce intramural debate not just over how conservative the party should be but also over the very definition of conservatism.

This debate wouldn't be as significant if it were limited to the candidates alone, but a growing number of conservative intellectuals have also surrendered to the oxymoronic notion that conservatism must adapt to survive as a powerful political force in this nation.

Former George W. Bush speechwriter David Frum is an example. In his new book, "Comeback, Conservatism That Can Win Again," he argues that Republicans need a new approach because they can no longer win elections on the conservative ideas that catapulted them to power in the 1980s.

Apart from Frum's book, which I've yet to read, conservatism faces serious challenges, owing to these (and other) factors:

• President George W. Bush, through his "compassionate conservatism" -- including its faith based initiatives, its greater federal role in education, its immigration policy and its excessive spending -- has diluted and muddled conservatism.

• Presidential candidate Mike Huckabee appears prepared to expand on Bush's compassionate conservatism to a degree even more objectionable to Reagan conservatives.

• There is a strong element of isolationism within the conservative tent, typified, variously, by Pat Buchanan and Ron Paul. A strain of protectionism, contrasted with Ronald Reagan's affinity for Milton Friedman-style free trade, is also present.

• There exists a purist neoconservative faction within the conservative movement. The difficulties this presents are compounded by antiwar liberals who portray this faction as much larger than it is. Continued...