Several Republican lawmakers are launching a counterassault against relentless Democratic attacks on personal investment accounts taken from Social Security (search) taxes.

"It's not a matter of if we reform Social Security, it's a matter of when and how we reform Social Security," said Nebraska Sen. Chuck Hagel (search), the first senator to offer a specific proposal to reform the retirement system.

Hagel introduced his plan Monday. It contains personal accounts similar to President Bush's proposal, but also includes a fix for the long-term solvency of the system.

On Tuesday, Hagel asked where the Democratic plans are.

"I hope the Democrats will be introducing some Social Security reform legislation. I have not heard them talk about their alternatives other than raising taxes," he said.

As Bush and other administration officials fan out across the country to talk about Social Security — making 60 appearances in 60 days — an outside group called Progress for America (search) made its biggest national ad buy thus far, promoting reforms.

"Some people say Social Security is not in trouble. Just like some thought the Titanic was unsinkable," the ad says.

The ad argues that with fewer workers contributing to the system and more workers heading toward retirement, Social Security will get deeper and deeper into financial problems.

Some Democrats concede something should be done but not necessarily soon. They also insist that personal accounts must be off the table.

"We're here today to urge Senator Hagel to drop privatization and to get the president to drop privatization and then we can sit down and talk," New York Sen. Charles Schumer, one of the Democrats' leading opponents to personal accounts, said during a press conference on Tuesday.

Republicans argue it's far too early to talk about what's negotiable and what isn't, and some of their proposals to fix the solvency of the system hold the promise of attracting bipartisan support.

One Republican plan taking shape allows wealthier taxpayers to receive reductions in future benefits while locking in higher benefits for low-income taxpayers. Some Democrats have indicated they find it an interesting measure.

Click in the box near the top of the story to watch a report by FOX News' Jim Angle.