MONTPELIER, Vt. (AP) — The Vermont Senate voted Wednesday to block the state's only nuclear plant from operating after its license expires in 2012, at least a temporary setback for nuclear power only a week after President Barack Obama announced loan guarantees for building two reactors in Georgia.

Vermont is the only state in the country with a law giving its legislature a say over a nuclear plant's relicensing. The Senate's 26-4 vote against a 20-year extension of Vermont Yankee's license marks the first time lawmakers have formally weighed in on the question.

With the Vernon reactor leaking radioactive tritium into groundwater and its owners accused of misleading state regulators about underground piping at the plant, even senators who might have supported the license extension said they would have a difficult time doing so now.

"If the board of directors and management were infiltrated by anti-nuclear activists, I do not believe they could have done a better job destroying their own case," said Sen. Randy Brock, R-Franklin, who had supported an amendment calling for building a new reactor in Vernon before he voted against the extension.

Wednesday's vote came after 3 1/2 hours of debate in a Senate chamber whose edges and balcony — along with two large hearing rooms equipped with live links — were jammed mostly with anti-nuclear activists hungry for a victory at a time when President Barack Obama has called for a resurgence of fission reactors as a source of electric power for the country.

Obama announced last week he was making about $8 billion in federal loan guarantees available for a facility envisioned for Burke County, Ga., which would be the first new U.S. nuclear power plant in nearly three decades. He said investing in nuclear energy is a "necessary step" toward reducing U.S. dependence on foreign oil.

Vermont Yankee and its owner, New Orleans-based Entergy Corp., were defiant after Wednesday's the vote.

"The effort to win a 20-year renewal of Vermont Yankee's operating license is far from over," company spokesman Larry Smith said in a statement. "We remain determined to prove our case to the Legislature, state officials and the Vermont public."

Entergy's shares fell 67 cents, or less than one percent, to close Wednesday at $76.33.

Senate President Pro Tem Peter Shumlin, whose Windham County district includes Vermont Yankee, summed up what he said was the case against the plant.

"Vermonters deserve better than an aging, unreliable nuclear power plant owned by an untrustworthy out-of-state corporation," said Shumlin, a Democratic candidate for governor.

The vote brought complaints from the administration of Gov. James Douglas, Vermont Yankee owner Entergy Corp. and its supporters that senators were engaged in a rush to judgment and a political attack on an operation weakened by news of its tritium leaks and misstatements.

Afterward, Douglas said the vote may not have much impact. If the state ends up with a more nuclear-friendly legislature after the November elections, lawmakers next year could reverse Wednesday's action.

"This vote in the Senate and all of the debate and the consideration over the past few weeks is little more than theater," the governor said.

Douglas, a Vermont Yankee supporter who has vetoed other bills the plant didn't like, won't get a chance to veto this one.

In order to become law, a bill must clear both the House and Senate and then be signed into law by the governor. A 2006 state law — signed by Douglas — contained a provision requiring an affirmative vote by both the House and Senate before state utility regulators would be allowed to issue the certificate of public good Vermont Yankee needs to operate past 2012.

The Senate's negative vote prevents the bill from being considered by the House — where its prospects would have been uncertain at best — and means Douglas won't see it.

The House could craft its own bill, but wouldn't bother if the intent were to support continued operation of Vermont Yankee, said Rep. Floyd Nease, D-Johnson, the majority leader. Nease said any such measure surely would die in the Senate.

"For the first time in my eight years here, I'm glad there's a Senate," Nease said with a smile.