President Bush's campaign to allow Americans to invest a portion of their Social Security taxes in the stock market is losing support among Republican congressional candidates, as Wall Street's sinking prices reinforce worries about the proposal.

Amid sharp attacks by the Democratic Party, several GOP incumbents and challengers are coming out against Bush's plan for partial privatization of the popular, taxpayer-funded retirement program. Fueling the shift is the stock market's recent plunge, which has reminded voters of the risks of investing in stocks, rather than in other financial instruments that guarantee safe but modest returns.

The president continues to call for giving workers the right to direct a portion of their Social Security payroll taxes to stocks or other investments by creating personal savings accounts. Bush first extolled the plan near the peak of the last decade's remarkable bull market; he says Wall Street's frequently impressive returns should boost Social Security as well as nongovernment retirement programs.

In some cases, GOP lawmakers such as Reps. George W. Gekas (Pa.) and Charles W. "Chip" Pickering Jr. (Miss.) are opposing Bush's proposal after praising it in the past. At least three Republican congressional challengers -- Rick Clayburgh (N.D.), William J. Janklow (S.D.) and Jon Porter (Nev.) -- have disavowed the idea of private accounts. Many other Republicans are playing down previous endorsements of privatizing all or part of Social Security as a way to bolster the system before it goes broke.

This retreat complicates Bush's campaign to revamp Social Security in the next Congress, which was a formidable challenge from the start. It also provides the latest example of how corporate scandals and the recent stock market swoon are altering public policy debates. If this signals the start of a broader defection, it could put pressure on congressional Republicans in the years ahead to articulate a new strategy for change.

Rep. Jim Kolbe (R-Ariz.), author of a bipartisan bill to create individual savings accounts, said some colleagues are "running for cover," making it more difficult for Congress to enact meaningful reforms.

"Politics always gets in the way of serious policy, and there are few issues where this is more true than Social Security," Kolbe said. "I think it's a mistake not to stick with the president's position."

White House spokeswoman Claire Buchan, rattling off a list of Republican candidates supporting the Bush plan, played down the defections. "While not everyone will agree on how to fix Social Security," she said, "we are pleased the president's proposals enjoy broad bipartisan support."

Even if the system is partially privatized, experts say, lawmakers will likely have to consider raising the eligibility age, cutting benefits for wealthy recipients or raising taxes to ensure there is enough money for baby boomers approaching retirement.

Most politicians are reluctant to endorse any of these solutions for the very reason some Republicans are backing away from Bush's private accounts: It's often tantamount to political suicide. As Democrats are proving once again, Social Security is perhaps the most lethal weapon in contemporary politics.

The reason is simple: Senior citizens, many of whom rely on the retirement program to pay rent and buy food, vote in large numbers.

Although corporate accountability was the hot topic in Washington in July, Democratic rhetoric on Social Security is often even hotter on the campaign trail in August, according to lawmakers and strategists in numerous races across the country. With many 401(k) retirement plans losing value because of their faltering stock holdings, Social Security checks are more important than ever to retirees and older workers. The idea of investing part of that money in the stock market, which looked so attractive when Wall Street was booming, now appears foolish to many seniors -- and politicians.

Democrats have launched another broad campaign to convince seniors that Republican policies are jeopardizing Social Security. In response, GOP incumbents and challengers are calibrating their positions to inoculate themselves against such attacks.

Before leaving town for the August recess, Republican lawmakers received a detailed dossier from their leaders warning them against talking about privatization. It instructed them to avoid staking out specific solutions to shore up Social Security. And despite Bush's campaign to win support for his proposal, it did not encourage GOP lawmakers to endorse the push for private accounts.

"Simply put, [older Americans] do not want the rules of the game to change," the dossier said.

Pickering, who faces Rep. Ronnie Shows (D-Miss.) in a redrawn district on Nov. 5, was one of 117 lawmakers to sign a letter last year saying Social Security reform must offer young workers the opportunity to improve their rates of return through personal retirement accounts. Now he says that's "not an option."

"When you have war, recession and market instability, I do not believe this is a time to change Social Security," he said.

Shows accused Pickering of undergoing an election-year conversion. "He's flipped, he's flopped," Shows said. "Just as soon as he gets reelected, he's going to jump back on the bandwagon with the president."

In Minnesota's 6th District, Rep. Mark Kennedy, a GOP freshman locked in a tough reelection fight, has tempered his support for creating private accounts. Although he signed the same letter as Pickering, he is campaigning feverishly to convince voters he has not switched his position.

After initially denying to local reporters that he signed the letter, Kennedy now will only say: "I support exploring ways of strengthening Social Security. I don't know what those ways are."

In Pennsylvania's 17th District, Gekas -- forced by redistricting to run against Democratic Rep. Tim Holden -- has come out strongly against Bush's plan. Gekas said Bush's inability to articulate how Americans would be protected against precipitous drops in stock values has forced him to oppose the plan.

"There's no place for it in the current debate," he said.

Two years ago, in a column to his constituents, Gekas praised personal retirement accounts. "[Social Security] money is yours and you should be able to determine how to make it work for you," he wrote in July 2000.

Gekas concedes there was some hyperbole in the column but insists he never explicitly endorsed the Bush plan. To emphasize the point, Gekas unexpectedly showed up at a political event hosted by Holden to put in writing his pledge to oppose privatization.

Republicans charge that Democrats are trying to scare seniors by misrepresenting Gekas's position (he has never voted to privatize Social Security) and exaggerating the voting records of other Republicans.

In several races, Democrats are accusing Republicans of supporting privatization because they voted to fund a bipartisan Social Security Commission, whose recommendations were expected to include partial privatization.

"To say that's a vote to privatize Social Security is just beyond the pale. It's concocted out of thin air," said Steve Schmidt, spokesman for the National Republican Congressional Committee.

Not just incumbents are running from Bush's plan. Janklow, the South Dakota governor now seeking his state's only House seat, on Friday put his opposition to private accounts in writing, too. Janklow joined Gekas as the only Republicans who have signed an anti-privatization petition circulated by the Campaign for America's Future, a liberal advocacy group.

In Nevada's new 3rd District, Republican state Sen. Jon Porter says he is "adamantly opposed" to private accounts after entertaining the idea in his campaign two years ago. "The more I look and the more I research, the more convinced I am that there should be one focus: to preserve and protect Social Security," he said.

And, in a new twist, some Republicans -- such as Clayburgh and Rep. John Thune (S.D.), who is running for Senate -- are attacking opponents for supporting privatization. Clayburgh, who hopes to unseat Rep. Earl Pomeroy (D-N.D.), has questioned why Pomeroy once backed President Bill Clinton's proposal to let the government invest some Social Security funds on Wall Street.

Pomeroy said in an interview that he would no longer push for such a plan, and would instead focus on shoring up Social Security by paying down the debt.

Thune will not say whether he supports the president's plan, but he has run advertisements attacking Sen. Tim Johnson (D-S.D.) for suggesting in the 1990s that the government invest some of the funds in the stock market. Johnson has said he no longer supports such a move, and has called the ads "an outrage" because they imply he still holds that position.