John McCain had a surprising but pleasant evening on Tuesday night - watching Mitt Romney go down to defeat in nearly every contest and encountering a newly victorious but ultimately unnominatable Mike Huckabee all across the Bible Belt.

McCain's successes so far reflect not only his appeal as a candidate but also the bankruptcy of the conservative agenda and political strategy that have steered the Republicans for many years.

McCain's victories have been chiefly a triumph of biography over ideology.

Blessed, in Romney, with an opponent who approaches the Platonic Ideal of Inauthenticity, McCain has racked up primary-season successes more because of the personal contrasts between the two candidates than because of differences of program. But his personal merits have yet to sway those Republicans who classify themselves in the polls as very conservative.

A more direct affront to the Republican strategy devised by Karl Rove - to build support within the party's right-wing base and then try to win over just enough moderates to carry elections - cannot be imagined.

McCain's whole campaign is anti-Rovian. His core supporters are Republican moderates and Republican-inclined independents, and then he picks off enough conservatives to prevail.

Even if he didn't have a history of rocky relations with various right-wing leaders, the very trajectory of his campaign would pose a threat to the conservative movement, notwithstanding that McCain is philosophically an heir to Barry Goldwater.

Moreover, McCain's successes have not been accompanied by an ideological reorientation within Republican ranks. The polls do not show any diminution of self-described conservatives within the party or any notable growth of the moderate faction.

Run out of agenda

So how have Republican conservatives managed to be on the losing end of so many primaries?

It's not just that the conservative vote has been split between Romney and Huckabee. It's also that conservatives have run out of agenda.

With his pre-emptive war and seemingly permanent occupation in Iraq, and his attempt to privatise Social Security, George W. Bush pushed American conservatism past the point where the American people were willing to go - pushed them, in fact, to the point where they recoiled at the conservative project.

And with that, American conservatism shuddered to a halt. In the 2005-06 congressional session, Republicans still controlled both houses of Congress, yet they introduced no major legislation.

Apparent

This exhaustion of conservatism has been apparent all along in the Republican presidential contest, where the chief point of agreement among the leading candidates has been to make permanent both the Bush tax cuts for the rich and our occupation of Iraq.

The conservative agenda has been winnowed down to supporting what remains of Bushism. That's not only a losing formula for November, it also means that intellectually, conservatism is running on empty.

Huckabee's legions have their own cause - a pious populism that doesn't have much sway in urban areas. But consider what animated conservatives' support for Mitt Romney, who has not suspended his campaign.

It's not that they warmed to his shifting agenda or his elusive charisma. They simply hate John McCain, who threatens their cosmology by waging a campaign that does not put them at the centre of the political universe.

That, certainly, is what animates Rush Limbaugh and the right-wing talkocracy, who feel their power ebbing with each McCain success.

Indeed, Romney's ability to continue in this race was almost entirely a function of the breadth of the animus toward McCain on the Republican right - and his ability to fund his own campaign.

In California particularly, conservatives' fear and loathing of moderates have been raised to new heights by McCain's most prominent endorser, Governor Arnold Schwarzenegger.

The Governor's proposals these days are far more likely to win the endorsement of Democrats in the state Legislature, while Republicans - furious at his policies and furious that he bypasses them to deal with the majority Democrats - scarcely consider them.

In McCain, California's insular conservatives, an embattled and shrinking minority in their own state, see a version of Arnold writ large.

Harold Meyerson is editor-at-large of American Prospect and the L.A. Weekly