Neither President Bush nor congressional leaders have put forth a bill to overhaul Social Security (search), but that won't stop the Senate from beginning its deliberations.

Two Democrats and two Republicans will square off Tuesday night in a mock debate on the Senate floor, arguing whether — and how, if necessary — the government retirement insurance program should be altered.

The leaders of the parties' respective policy committees, Sens. Byron Dorgan, D-N.D., and Jon Kyl, R-Ariz., decided to engage in the exercise as a likely precursor to the real thing later this year. The committees previously sponsored a debate on the subject in 2003.

"These debates are an opportunity for us to rise above 30-second sound bites for a true give-and-take on important issues in a way that the Founding Fathers (search) might have envisioned," Kyl said in a statement. "Rather than watching scripted speeches read to a mostly empty chamber, the American people will have a chance to hear strong, but civil, disagreements, and maybe, on occasion, find areas where our parties agree."

Dorgan said separately: "There is no more important domestic issue than ensuring the future of Social Security."

Democrats have tapped Sens. Dick Durbin of Illinois and Debbie Stabenow of Michigan to prosecute their case. The Republicans, meanwhile, have selected Sens. Rick Santorum of Pennsylvania and Jim DeMint of South Carolina.

The debate, scheduled to begin at 6 p.m. EDT Tuesday, will be broadcast nationally by C-SPAN. It is expected to last about an hour.

Bush has proposed transforming the Depression (search)-era program by allowing younger workers to divert income equivalent to 4 percentage points of the 12.4 percent payroll tax that funds Social Security into a personal investment account.

The administration argues such accounts have the potential to offer greater payments to retirees, plus offer an inheritable asset should a worker or retiree die. Critics say the effort to create the accounts is a veiled attempt to kill Social Security by starving it of the money needed to provide traditional benefit checks.

Both sides agree that the accounts will not solve the program's long-term solvency issues.

Bush is scheduled to stump for his proposal Tuesday in a visit to Parkersburg, W.Va., where the government holds IOUs that comprise the Social Security trust fund.

Santorum, who just held a series of Social Security town hall meetings on college campuses during the two-week Easter congressional recess, said the challenge for the administration is reaching younger workers. The president has already said any changes will not affect workers aged 55 or older.

"That to me is really going to be the key," Santorum said Monday during a conference call with reporters. "Are the folks who are going to be affected going to ante up?" The senator said he thought they would.