"The federal government should not be running the used car business. This is a horrible policy idea," DeMint told ABC News. "And the fact that people buy cars when you give them free money does not mean that is what the federal government should be doing."
Sen. John McCain, R-Ariz., argued the program is a boondoggle and amounts to another bailout of the auto industry.
The White House says taxpayers will not have to foot the $2 billion bill because it will come out of the stimulus budget.
Thanks to the Cash for Clunkers program, 39 percent of trade-ins qualify as clunkers, compared to 9 percent prior to the program, according to Edmunds.com.
The program was supposed to run until Nov. 1 or when the money ran out, whichever came first, but it was so widely popular that funds ran out within a week of its initiation.
Americans can get a rebate ranging from $3,500 to $4,500 if their car meets the requirements. Some of the key facts to know are:
- Trade-in vehicles have to provide 18 miles per gallon or less to be eligible, but some trucks and cargo vans have different requirements.
- Cars have to be less than 25 years old on the date it is traded in.
- People trading in their clunker have to buy or lease a new vehicle.
- The vehicle must be insured and registered for the full year preceding the trade-in.
- The cars being traded in cannot be resold or restocked and have to be scrapped.
Six of the cars in the top 10 list are by foreign manufacturers, including Toyota, Honda and Hyundai.
ABC News' Charles Herman contributed to this report.