The Social Security (search) system will take in more money annually than it pays out in benefits until 2020, two years later than earlier estimated, the Congressional Budget Office (search) reported Monday in a modest change unlikely to alter the growing political debate over the program.

Congress' budget analysts also estimated the program's trust funds will be depleted in 2052, "meaning that beneficiaries will be able to count on receiving only 78 percent of their scheduled benefits beginning then.

"After the trust funds are exhausted, Social Security spending cannot exceed annual revenues," the analysts said. "As a consequence ... benefits paid will be 22 percent lower than the scheduled benefits."

In both cases, the CBO estimates are more optimistic than the most recent projections made by the Social Security Board of Trustees (search). In the annual report it issued last March, the board said annual income would fall behind benefit payments beginning in 2018, and the trust funds would be empty in 2042.

Bush has cited the trustees' estimates as evidence of a need for legislation to place Social Security on a permanently stable financial footing. The president also wants to give younger workers the option of setting aside a portion of their payroll taxes into personal retirement accounts. Aides have also indicated the administration may propose reducing the starting benefit for future retirees by as much as 40 percent.

Republicans have been girding for a political battle over Social Security, and their critics have begun to deploy their forces, as well.

MoveOn.org, which claims 3 million members nationwide, announced Monday it would run television commercials in three key House districts and on cable television in Washington and New York as part of an effort to build opposition to Bush's recommendations.

The organization, which said it raised nearly $10 million during last year's political campaign, said it intends to broaden its advertising effort in the future.

Another organization, the National Women's Law Center (search), issued a state-by-state report estimating that benefit cuts for future retirees would fall particularly hard on widows under an option that administration officials are studying.

"Nationally the typical widow receives a benefit of $865 per month, but under the leading privatization plan, the benefit, including the proceeds of the private account, would be only $476 per month," the group said in an accompanying statement. "This amount is equal to only 65 percent of the poverty line."

The organization said the average benefit for widows would be lower in Arkansas and North Dakota, two of the states Bush is scheduled to visit in the days after Wednesday's State of the Union address.

Despite the attacks, Bush and officials in his administration have sought to reassure congressional Republicans that the voters are ready to embrace changes in Social Security.

Members of the GOP House and Senate rank and file who attended a closed-door retreat over the weekend received a booklet designed to help them navigate the political terrain. It includes sample speeches for lawmakers to use while talking with their constituents about the issue.

"Without action the benefits will certainly be cut dramatically, long before today's high school graduates are ready to retire," one suggested speech says.