LINCOLN, Neb. (AP) — Nebraska's Republican lawmakers were thwarted Tuesday in their attempts to reinstate a winner-take-all system for presidential electors, a move that would have increased the GOP nominee's chances of winning all five of the state's votes in November.

The effort was derailed after supporters failed to overcome a legislative filibuster, just as they were on the brink of approving it. Had it passed, the bill would have ended the state's practice of allocating its electoral votes by congressional district.

Nebraska and Maine are the only states where it's possible to divide electoral votes between opposing presidential candidates in a general election. The states award one electoral vote to the winner of each congressional district, and the other two to the statewide winner. California allocates its electoral votes by district in Republican primaries.

Nebraska split its electoral votes for the first time in 2008, when Obama captured one from the 2nd congressional district in Omaha on his way to the presidency.

The bill gained unusual traction this year, advancing through two of three required rounds of voting in the Legislature. It failed on Tuesday after two Republican lawmakers who had previously cast procedural votes to let it move forward changed their minds. Senators voted 32-17 to force an end to debate, one vote shy of what was required to keep the bill from dying.

Republicans argued that no state has followed Nebraska since it adopted the system in 1991, largely on the belief that it was leading a movement.

"It's been 25 years, and there's no state that even come close to passing this," said Sen. Robert Hilkemann, an Omaha Republican. "I think it's one of those experiments that it's not working."

After the vote, Republican Gov. Pete Ricketts said he wished the bill had passed, "but it's an issue that comes up every year." Sen. Beau McCoy, the bill's sponsor, said he's confident senators will debate a similar proposal next year.

Democrats and even some moderate Republican senators opposed the bill, saying it would reduce the incentive for urban voters to participate in an overwhelmingly rural, conservative state.

The winner-take-all system "will result in no-choice elections where one party has a permanent monopoly on power," said Sen. Tanya Cook, an Omaha Democrat.

Adopting a similar model on a national scale would dramatically change the way Americans elect their president. In the current political climate, it could put Democrats at a disadvantage in states where Republican legislatures drew congressional district lines to give their party an edge.

In Pennsylvania, a bill floated by a leading state Senate Republican won support from then-Gov. Tom Corbett in 2011. Critics argued that awarding votes from the state's gerrymandered congressional districts would reduce voter turnout and destroy Pennsylvania's status as a battleground in presidential races.

Virginia lawmakers introduced a GOP-backed proposal shortly after Obama won the state in 2012, but Republican Gov. Bob McDonnell voiced opposition to it and the measure died in committee. Similar legislation in Wisconsin and Michigan never gained traction.

Nebraska rarely sees presidential hopefuls, but in 2008 Omaha was visited by Obama, Republican John McCain and his running mate, Sarah Palin.

It's one of the safest locks for Republican presidential nominees, who haven't lost the statewide popular vote since Democrat Lyndon B. Johnson carried it in 1964. The 2nd congressional district, encompassing Omaha, is the only place where Democratic contenders stand a realistic chance of winning.

Nebraska adopted its current system in 1991 despite a Republican majority in the officially nonpartisan, one-house Legislature. Republicans have since tried a dozen times to repeal it.

Supporters in 1991 argued that allocating the votes by district was fairer and more proportional to urban voters in the overwhelmingly rural, conservative state, said former state Sen. DiAnna Schimek, who sponsored the bill to create the current system.

"My argument was that people would feel their vote was represented," said Schimek, a Democrat. "I thought it would inspire more people to get involved."

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Associated Press writer Anna Gronewold contributed to this report.

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