Senate Democrats pulled climate change legislation from the floor Friday after failing to garner enough support to push the bill toward a final vote.

Debate began on the Climate Security Act Monday, but bipartisan squabbling pushed the two sides into a deadlock that lasted four days, with each side blaming the other for inaction. Democratic leadership called for a cloture vote Friday morning, the only way to overcome a Republican filibuster, but fell 12 votes short of the required 60. With 16 senators absent, including presidential hopefuls Sens. Barack Obama, D-Ill., and John McCain, R-Ariz., the Senate rejected the move by 36-48.

Six senators who did not show up for the vote sent letters expressing their support. Had they been there, the vote in favor would have reached 54.

Although the bill came to the floor Monday, debate over amendments was blocked by political tactics. Minority Leader Mitch McConnell, R-Ky., requested Wednesday that the 492-page bill be read in its entirety -- an exercise that took more than eight hours, stalling debate on the floor. On Thursday the Democrats retaliated; Majority Leader Harry Reid, D-Nev., "filled the amendment tree" -- a process that prevented voting on amendments to the bill.

Finger pointing ensued on both sides.

"Our only request is that you let us debate amendments and vote on amendments," Sen. James Inhofe, R-Okla., said to Democrats Thursday. "It's a reasonable request."

But the amendments filed by Republicans were thinly veiled attempts to kill the bill, not serious efforts to revise it, a Reid spokesman told United Press International.

"They only had poison pills," he said.

Democrats accused Republicans of filibustering, then pulled the bill from the floor today after failing to invoke cloture, which would have limited debate in the following days.

The legislation represents the most recent attempt in Congress to establish a carbon trading scheme, whereby greenhouse gases are capped at a certain level and then businesses must buy allowances from the government in order to emit carbon dioxide and other climate-changing gases. Emitters could purchase additional allowances from entities that spewed less carbon dioxide than their share.

If it had passed, the bill would have cut U.S. emissions to 70 percent of 2005 levels by 2050.

The number of senators voting in favor today demonstrates growing enthusiasm for a cap-and-trade system in Congress, Sen. Barbara Boxer, D-Calif., said after today's vote.

"We had 54 senators come down on the side of tackling this crucial issue now -- because it is one of the greatest challenges of our generation," Boxer said. "This strong vote is up from 38 votes in 2005, and proves that our nation is ready to assume the mantle of leadership on global warming."

But opponents of the bill argue an emissions cap would strike a devastating blow to the economy -- raising utility bills and gas prices -- and set up a huge government bureaucracy to track emissions and auction allowances.

"The economic impacts of this bill are staggering," Sen. Wayne Allard, R-Colo., said on the Senate floor Thursday.

Allard pointed to an analysis conducted by the Heritage Foundation, a conservative think tank, that projected the bill would lead to a total loss in Gross Domestic Product of at least $1.7 trillion by 2030.

Proponents flatly deny these negative outcomes, and other analyses support their side as well. Instead of harming the economy, said co-sponsor Sen. Joe Lieberman, I-Conn., a cap-and-trade system would boost American business into a new green era by weaning the United States off foreign oil and encouraging the development of clean technology.

"If we adopt this bill, by 2025 we will be using 8.6 million barrels of oil less per day," Lieberman said earlier this week at a news conference. "Think about what that reduction in demand would do for the price of oil."

Even if the bill had passed, though, President Bush promised to veto it.

However, the bill's sponsors say they intend to move forward with the legislation next year, when the next president is in office.

"I am confident that the next Congress will pass and the next president will sign into law legislation addressing this critical problem," Lieberman said after Friday's vote.

The nominees for both political parties have expressed support for cap-and-trade legislation. McCain joined with Lieberman in 2005 to co-sponsor legislation that would have established a carbon-trading system, and both Obama and McCain sent letters of support for the Climate Security Act, as did former White House contender Sen. Hillary Clinton, D-N.Y.

In the end, the bill's demise is not surprising, and many political analysts expected it all along, said Philip Clapp, deputy managing director of the Pew Environment Group, a non-profit policy organization. The main purpose of the exercise was for senators to test out the waters at home, Clapp told UPI.

"What they're all recognizing is that this is the pilot project of next year's debate," he said. "(Because of) the position they take now, they will be subject to attack for a year before they go into the next debate."