The plan has been hit hard in recent years by large increases in tuition and small returns on its investments.
More than 6,400 people have invested $124 million in the plan.
Republican Gov. Mark Sanford wants to close the plan to new participants and pump in $41 million for current enrollees.
The Tuition Prepayment Plan is one of two programs offered by the state to help parents pay for their children's education. It lets families lock in a guaranteed tuition cost by paying in advance.
If the plan becomes insolvent, which is projected to happen by 2017, it would be liquidated and enrollees' contributions would be refunded with 4 percent interest from the General Fund, state Treasurer Thomas Ravenel said.
State Rep. Bob Leach, R-Greer, bought into the plan for his two grandchildren. Both want to attend Clemson University, which has the highest tuition of any state institution.
A refund of his investment plus 4 percent "won't make up for the tuition increase," he said.
That, critics of the plan say, is exactly the problem.
"College tuitions are rising too quickly for this program to be effective," Sanford spokesman Joel Sawyer said.
Mr. Sanford's proposed $41 million bailout reflects figures at end of calendar 2005, but the actuarial deficit grew to $63.8 million when the fiscal year closed June 30, according to the state Treasurer's Office, which administers the program.
Attempts to amend the plan have not fared well. A new bill in the state Senate would close the plan to new participants.
"We need to stop the bleeding," said state Sen. Greg Ryberg, R-Aiken, who co-sponsored the bill with state Sen. Kevin Bryant, R-Anderson.
The program could recover if tuition increases continue to slow as they did last year, and if investment return continues to grow as it has since July, said Paige Parsons, the state's senior assistant treasurer.