President Bush's proposal to overhaul Social Security is falling flat across the country, to judge from recent polls, but public opinion is not his only problem. The whole idea splits Bush's party -- along fault lines he masterfully bridged during his first term in the White House.

A Social Security overhaul is the Holy Grail for the GOP's free-market advocates, but it is a low priority for social conservatives who care more about banning abortion and same-sex marriage. The costly initiative gives heartburn to the party's antideficit hawks. Even some of the Republicans' loyal business allies are lukewarm on Bush's effort to rewrite the program and allow workers to divert part of their Social Security payroll taxes into personal retirement accounts.

 The divisions highlight potential weaknesses in the GOP coalition that Bush hopes to turn into an enduring governing majority by the time he leaves the White House.

On Capitol Hill, the open disagreement among Republicans over the issue -- and over the political strategy for dealing with it -- is a departure from the unity and discipline they showed on most major issues during Bush's first term.

* Economic conservatives

The party's most enthusiastic supporters of personal accounts are in a faction of conservatives whose top priority is advancing free-market concepts in the economy and reducing the role of government. The personal account idea has been nurtured for decades in conservative think tanks such as the Cato Institute and the Heritage Foundation. It has been promoted by groups such as Americans for Tax Reform and the Club for Growth.
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They believe that neither benefit cuts nor tax increases are needed to shore up the system and pay for the costs of switching to personal accounts. And, unlike Bush and his senior aides, they argue that personal accounts alone can solve the program's long-term financial woes. Opponents of this faction refer to them as the "free lunch crowd."

* Tax iconoclasts

Other Republican proponents of personal accounts are more willing to challenge their party's anti-tax orthodoxy or to consider benefit cuts to shore up the program. Sen. Lindsey Graham (R-S.C.) has proposed raising from $90,000 to $200,000 the cap on income that is subject to the Social Security payroll tax. Bush has left open the door for that option. Sen. Rick Santorum (R-Pa.) has also said Congress could consider raising the tax rate.

But the party's most ardent tax cutters -- a large and vocal faction that dominates the House GOP and outside conservative groups -- have tried to slam the door on any such tax increases.

* Antideficit hawks

Although Republicans are no longer as dedicated to balancing the budget as they once were, there is a vestigial faction that is concerned about the large and growing budget deficit. These Republicans -- mostly self-described moderates -- are among the most stubborn skeptics of Bush's personal account plan. Winning them over may require Bush to find some way to finance the transition costs other than piling up more debt.

That is the main reservation voiced by Sen. Olympia J. Snowe (R-Maine), co-chair of the Senate's Centrist Coalition, an informal bipartisan group exploring alternatives to Bush's plan. No members of the Republican Main Street Partnership, a group of House and Senate GOP moderates, have embraced the personal account plan.

"They are on hold," said Sarah Chamberlain Resnick, executive director of the group, mostly because of their concerns about the potential cost.

* Social conservatives

Conservative religious activists and voters whose top priorities are social values were key to Bush's reelection in 2004, many analysts say. But changing Social Security is not as important as banning abortions and same-sex marriage to the organizations that represent those interests, such as the Family Research Council and Concerned Women for America.

"I don't think we have come to a consensus," said Amber Hildebrand, spokeswoman for the Family Research Council.

* Business community

Trade associations and business lobbyists have been rallying to help Bush sell his Social Security policy, even though they probably would not have made this a top priority absent a push from the White House. They have required more coaxing than when they were tapped to promote Bush's tax-cut initiatives, administration allies say.

"Social Security is an issue we believe the president is right on, but it's not a no-brainer the way tax relief was a no-brainer for our people," said Jade West, senior vice president of government relations at the National Assn. of Wholesaler-Distributors.

Many experts believe Congress, whether by trimming benefits, raising taxes or other means, will act in time to keep Social Security from tumbling off a cliff in 2042.