Nothing succeeds like success and nothing fails like failure.

In politics, this means that if a leader is seen as doing well, his side in the debate holds together and suppresses disagreements that are quite real but don't seem worth pursuing if they get in the way of winning.

It also means that if a leader is perceived as doing badly, those quite real disagreements are seen as much more important. Parts of the leader's political coalition try to disengage themselves from the perceived failure and differentiate themselves from those whom they see as incompetent and thus representing something other than the true faith.

Former president Jimmy Carter knows what this is like. He faced rebellions on the left and right wings of the Democratic Party in 1980. The left went with Ted Kennedy when he challenged Carter in the Democratic primaries. The right defected to Ronald Reagan that fall in the great neoconservative rebellion. The first President Bush had solidarity going for him in 1988 -- the economy was strong and he was seen as continuing Reagan's successful presidency. By 1992, when Bush looked like he was a goner, conservatives were saying the president wasn't conservative enough. Moderates said he wasn't moderate enough. Unfair, perhaps, but unsurprising.

The beginnings of a conservative crackup under this President Bush flow directly from the perceived failures of his policies in Iraq. Whatever one's view of the war, things are not going as promised, or as hoped for. Bush dominated politics in the months after Sept. 11. Almost everything he said or did then was seen as a sign of strength and fortitude. Now when he does the same things, they are seen as signs of stubbornness and a lack of reflection. The line between the virtues and the flaws is slim, and decisive.

And that means that solidarity -- a characteristic of the conservative movement for the past three decades except for interludes under Richard Nixon and the first George Bush -- is fraying. Lacking unity, conservatism is expressing its variety.

There are, first, the traditionalist conservatives, the most authentic of the breed. They are skeptical of large projects undertaken by government to improve humanity because they don't fully trust either government or humanity. It is our fate to live with imperfection and it is wise to be mistrustful of utopia.

It is this view that has made the columns of George Will, my conservative colleague, so powerful over the past few months. Will in no way sounds like a liberal in criticizing Bush's war in Iraq. "Conservatives are not supposed to be especially nice," he wrote recently. "They are bleak, flinty people given to looking facts in the face; hence, they are prone to pessimism." In this telling, the Iraq venture looks more like exporting the Great Society's community action program to Tikrit than a policy rooted in conservative realism.

But the neoconservatives who deeply believe in the purposes of this war are not happy either. They can't understand how the administration could botch such an essential project. Why, they ask, were more troops not sent to Iraq at the beginning to get the place under control? Why has there been such a reluctance to smash opposition to the American venture in Iraq, to "give victory a chance," as William Kristol wrote recently in the Weekly Standard?

The isolationist conservatives around Pat Buchanan cannot understand why we went to war in the first place -- and they opposed it from the beginning. These conservatives speak explicitly about the "costs of empire," much as the left does. They argue that globalism is really "globaloney" and that being an empire is incompatible with being a republic.

With the splits on Iraq exposed, other splits within conservatism become more obvious. Small-government conservatives feel ever more free to speak out against the large budget deficits over which Bush has presided. Anti-immigration conservatives speak out against the president's immigration policies. Pro-military conservatives criticize Defense Secretary Donald Rumsfeld's dominion over the Pentagon, reflecting the views of many in the military brass who never much liked Rumsfeld or his plans.

Yes, Bush's problems have something to do with his declining poll ratings. Trouble in politics breeds more trouble. A bit more stability in Iraq could breed a bit more stability in the conservative movement. Bush has to hope so, because it's hard to win reelection when you have to put out so many fires in your own back yard.