The vote was 24-10. The measure went to the House, which also was expected to pass it and send it to Gov. Kathleen Sebelius.

But most legislators expected her to veto it because she already has rejected two other bills that would have cleared the way for the plants. All three measures also restrict the power of the regulator who has been blocking their construction for nearly seven months over concerns that they will contribute to global warming.

Supporters hope to attract the two-thirds majorities in both chambers to override a veto. Their latest tactic was to include proposals designed to encourage other projects, including a transportation hub in Johnson County.

The coal plants enjoy bipartisan support because many legislators view them as economic development. The new bill is even called the "Economic Stimulus Act of 2008."

"You have to have infrastructure if you're going to have economic development," said Senate Commerce Committee Chairwoman Karin Brownlee, an Olathe Republican who supports the coal plants.

But Sebelius already has questioned whether the measure violates the Kansas Constitution's prohibition on bills containing more than one subject. Senate Judiciary Committee Chairman John Vratil, who has voted consistently for the coal plants, said he couldn't support the latest bill for that reason.

The margin in the Senate was three votes short of a two-thirds majority, but six senators, including five supporters of the plants, were absent. Bills allowing the plants have passed with as many as 33 votes.

"I cannot vote for a bill that I believe is unconstitutional," said Vratil, a Leawood Republican and an attorney.

Sunflower Electric Power Corp. wants to build the two plants outside Holcomb, in Finney County, and sell 86 percent of the power to two out-of-state utility partners.

In October, Rod Bremby, the governor's secretary of health and environment, denied an air quality permit for Sunflower because the plants could produce up to 11 million tons of CO2 a year. Many scientists link such man-made greenhouse gases to climate change.

Sunflower's legislative allies always have remained short of votes in the House to override Sebelius' vetoes.

"The governor's concerned that this isn't constitutional with the jumbling of issues," spokeswoman Nicole Corcoran said of the latest bill. "It still holds the same key elements that she's opposed to."

Sunflower's supporters have tried to lure the necessary votes by adding "green" provisions. They have included a mandate that renewable resources, such as wind, account for 20 percent of most utilities' generating capacity by 2020 -- and a requirement that Sunflower meet the standard by 2016.

Earl Watkins Jr., Sunflower's chief executive officer, endorsed bundling his company's project with the others.

"I can certainly see the logic behind the leadership saying all of these matters have an economic development undertone," he said.

But Senate Minority Leader Anthony Hensley, a Topeka Democrat, called the bill a transparent attempt to trade votes in "a high stakes game of poker."

"Enough is enough," he said. "Quite frankly, I resent it."

After voting against the bill, Hensley filed a written protest questioning the measure's constitutionality.

But House Judiciary Committee Chairman Mike O'Neal, a Hutchinson Republican and an attorney, said he believes the measure will withstand a legal challenge.

"It's a very hard argument to win," O'Neal said. "I found, like, one case out of 40 or 50 in which the issue came up in which the court actually found that it violated the two subject matter rule."

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Coal plants measure is Conference Committee Report for HB 2412.

On the Net:

Kansas Legislature: http://www.kslegislature.org

Governor's office: http://www.governor.ks.gov

Sunflower Electric Power Corp.: http://www.sunflower.net

Opponents of Sunflower's project: http://www.KansasCleanEnergy.com