Harkin's failed amendment, formally called "The Sell Fuel Efficient Cars Amendment," parallels a bill introduced by Sen. Dianne Feinstein, D-Calif., called the "Accelerated Retirement of Inefficient Vehicles Act" (S. 247), which she worked on last session with former Sen. Ken Salazar, now President Obama's Secretary of the Interior. Both the amendment and bill provide rebates to those who trade-in gas guzzlers for new or used autos (Harkin specifies only "new" U.S.-made autos) whose Corporate Average Fuel Economy (CAFE) rating is above a certain level. The old car must be scrapped with their key auto parts banned from coming back into the reclaimed parts market. The rebate of $10,000 per trade-in is limited by individual and family adjusted gross income levels.

It is not clear why Harkin withdrew the amendment. But the Senate had already accepted an $11 billion auto purchase incentive amendment from Sen. Barbara Mikulski, D-Md., which allows consumers who purchased new cars between November 2008 and December 2009 to get a tax deduction.

Mikulski's amendment was more politically palatable than Harkin's, which was opposed by foreign automakers with assembly and manufacturing plants in the U.S. "The Harkin Buy American amendment clearly violates the WTO & NAFTA trade agreements," states Barbara Nocera, director of government and public affairs at Mazda North American operations. "And, furthermore, it smacks of the type of protectionism that led to the Great Depression."

Wade Newton, spokesman for the Alliance of Automobile Manufacturers, which includes the Detroit Big Three and foreign companies, says, "I don't know if we opposed the Harkin amendment. But it is safe to say that on principle we think that any fleet modernization program ought to be fair to all automakers."

It should be noted that when the House and Senate agreed on a final stimulus package, the Mikulski amendment was stripped down to $1.7 billion, allowing new car buyers to deduct the state sales and excise taxes from the purchase, but not the interest on the loan, as was originally proposed.

Vehicle scrapping programs are also popular with environmentalists, who are an important part of the Democratic base. The American Council for an Energy-Efficient Economy is a major backer of the Harkin and Feinstein proposals, which are already in operation in some states. Andrea Morrow, spokeswoman for the Texas Commission on Environmental Quality, says her state's "Drive a Clean Machine" program debuted in December 2007. Consumers can get up to $3,500 for old cars located in any of 16 Texas "Clean Air non-attainment" counties.

Stephen Barlas has been a full-time freelance Washington editor since 1981, reporting for trade, professional magazines and newspapers on regulatory agency, congressional and White House actions and issues. He also writes a column for Automotive Engineering, the monthly publication for the Society of Automotive Engineers.