Lawmakers voted 49-49 for Sen. Debbie StabenowDeborah (Debbie) Ann StabenowHere's evidence the Senate confirmation process is broken Schumer: Democrats considering option to pay for all of infrastructure agenda Democrats closing in on deal to unlock massive infrastructure bill MORE’s (D-Mich.) amendment to transportation legislation, but 60 votes were needed for approval.

The vote signals political hurdles facing advocates of green-energy tax breaks, notably the production tax credit for wind power projects that's expiring at year's end, an incentive that's crucial to financing new development.

The number of new wind projects brought online has dropped sharply when the credit has been allowed to lapse in the past.

Stabenow’s plan would have also extended various incentives for energy efficient homes and appliances, plug-in vehicles, production of certain biofuels and a program that provides grants in lieu of tax credits for renewable power, among others.

But while the Senate didn’t extend the green-energy tax breaks, lawmakers also rejected Sen. Jim DeMint’s (R-S.C.) amendment to kill a range of energy-related tax incentives.

His plan, defeated 26-72, would have repealed a suite of tax credits for green-electricity projects, plug-in cars and renewable transport fuels, as well as some for oil-and-gas companies, while applying the savings to a commensurate cut in the corporate tax rate.

DeMint argued for the amendment along ideological lines on Tuesday, saying that Congress ought not to be choosing winners and losers within the energy industry. 

"If we let the market work we are going to have wind and have solar anyway … this is no way to try to run a free market economy, to try to run it from this room," he said.

—This story was updated at 3:30 p.m. to reflect the defeat of the DeMint amendment.