In a nail-biter, Senate Democrats on Thursday narrowly beat back a Republican attempt to scuttle a measure designed to spur new car buying.

By a 60-36 vote, Democrats succeeded in keeping the “cash for clunkers— provision in the $106 billion supplemental war spending bill. Sixty votes were needed to waive points of order against the bill.

Four Republicans — Sens. Kit Bond (Mo.), Thad Cochran (Miss.), George Voinovich (Ohio) and Susan Collins (Maine) — voted with most Democrats to retain the provision and other portions of the bill that could have been struck because they violated the rules for conference reports and emergency legislation. Sen. Ben Nelson (Neb.) was the lone Democrat to vote against his party.

Sen. Maria Cantwell (D-Wash.) initially voted with Nelson, but switched her vote when it was apparent Democrats would not prevail without her. Senate Majority Leader Harry Reid (D-Nev.) and other Democratic leaders could be seen on the Senate floor cajoling Collins and Sen. Roger Wicker (R-Miss.) to vote to waive the points of order. Collins and Wicker waited to cast their votes until the very end.

A visibly angry Sen. Tom Harkin (D-Iowa) was lobbied by Sens. Debbie Stabenow (D-Mich.), a key proponent of the provision, as well as Appropriations Chairman Daniel Inouye (D-Hawaii), before he irately stuck his thumb in the air to vote “aye.—

Republicans had objected to the $1 billion cash for clunkers program, which would provide vouchers to car buyers who trade in for a more fuel efficient model, because the cost was not offset. Other Senators, such as Collins and Cantwell, were concerned that the measure did not set fuel efficiency standards for qualifying vehicles high enough to have an effect on the environment.

Collins along with Sen. Dianne Feinstein (D-Calif.) have sponsored a separate measure calling for tougher fuel efficiency standards for new car purchases under the program.

Feinstein said she and Collins were promised any extension of the current program would reflect their legislation.

“I’ve received a commitment from leadership that this will be a four-month bill,— Feinstein said. “And the next bill they bring up will be my bill.—

Stabenow said she was always under the impression that the program would be enhanced with stronger fuel efficiency standards.

Knowing they would have a close vote, Democrats used a procedural maneuver that forced the Senate to vote to waive all points of order against the supplemental, rather than voting on a planned Republican point of order against cash for clunkers only.

The provision violated rules prohibiting conferees from inserting legislation that was in neither the House nor Senate version into conference reports. Other points of order might have eliminated funding items not related to the wars in Iraq and Afghanistan, because it was not considered “emergency— funding.

The Senate is expected to vote later Thursday afternoon or evening on final passage of the supplemental.

Jessica Brady contributed to this report.