Once seen as a long-shot darling of liberals, a bill that would allow Louisiana voters to decide whether they want to require unanimous jury verdicts in all felony trials now has a real chance of clearing the Legislature, thanks to its surprising appeal among many conservatives.

The bill has only one significant hurdle left, though it's a big one: It must be approved by two-thirds of the 105-member state House. That means it needs 70 votes in support, regardless of how many members actually vote.

If the bill passes, a measure to amend the state Constitution will go on the Nov. 6 ballot. At the polls, passing it would require only a simple majority of voters -- though that could prove even more difficult than getting it through the Legislature.

No move to undo Louisiana's unusual practice of allowing convictions with only 10 of 12 jurors' votes has ever before gained serious traction. But the bill narrowly cleared the Senate with the required two-thirds majority last month, surprising even its author, Sen. J.P. Morrell, D-New Orleans. Its momentum has since snowballed.

That's because proponents have built a coalition that now spans both ends of the political spectrum, with the conservative Koch brothers and the Louisiana Family Forum recently declaring their allegiance.

Louisiana's powerful district attorneys initially took a strong and united stance against the bill, but they have dropped their official opposition -- though some individual district attorneys have continued to beat the drum for the status quo.

The rule allowing for split juries was the product of Louisiana's notoriously racist 1898 constitutional convention, which was convened in part to "restore the supremacy of the white race in Louisiana." In large part, this was done by trying to remove the vast majority of black residents from the state's voting rolls -- lists that were, and still are, used to create pools of prospective jurors.

The original rule, unique in the country, required that just nine of 12 jury members had to agree before a verdict -- whether guilty or not guilty -- can be rendered. The threshold was raised to 10 out of 12 in 1974.

While some of the current system's backers argue that the law was cleansed of its racist origins with that update, a yearlong investigation by The Advocate found that it nonetheless continues to exert racially disparate effects.

In part, that's because defendants in Louisiana are disproportionately black, while the juries that sit in judgment of them tend to be whiter than the communities from which the members are drawn.

The newspaper found that split verdicts are 30 percent more common when the defendant is black. And an analysis of jury votes in East Baton Rouge Parish found that in cases without unanimity, black jurors were 2.5 times more likely to dissent from the majority verdict than white jurors.

The law's dubious Jim Crow origins and its ongoing discriminatory impact have made Morrell's bill a popular one for the Legislative Black Caucus.

But rather than focusing on the law's unfortunate racial aspects, Morrell, who is African-American, has instead sought to emphasize how current law conflicts with longstanding American legal traditions cherished by the framers of the U.S. Constitution.

Helping Morrell make the "originalist" case has been Ed Tarpley, a conservative former district attorney from Grant Parish and now a passionate advocate for changing the split-verdict law.

Both Tarpley and Morrell, in committee testimony, have harped on the importance of jury unanimity in American jurisprudence, saying that James Madison and John Adams, both architects of the republic, were hard-liners on jury unanimity. So, too, they note, was the late Supreme Court Justice Antonin Scalia, beloved among conservatives.

Tarpley quoted a 2004 Scalia opinion in which the justice wrote: "The framers would not have thought it too much to demand that before depriving someone of his liberty, the state should suffer the modest inconvenience of submitting the accusation to the unanimous suffrage of 12 of his equals or neighbors."

Tarpley added: "This is Justice Antonin Scalia," whom he called "the greatest conservative justice in the recent modern era."

The rationale seemed to go over well with some of the House Committee on Criminal Justice's 10 Republican members. State Rep. John Stefanski, R-Crowley, for instance, told Tarpley and Morrell that he had read that opinion and he had "long been an admirer" of Scalia's.

Scalia's imprimatur also has proved to be persuasive to other conservative groups, including Americans for Prosperity, the influential libertarian-leaning organization associated with the billionaire Koch brothers, which is urging members to support the bill.

"As far as justices are concerned, I don't know if you can get any more conservative than (Scalia)," said John Kay, an AFP lobbyist in Baton Rouge.

Requiring unanimous verdicts is "limited government in its purest form," Kay said. "We believe in keeping government from your property and from your life and liberty. Of course, there are instances when someone should be put in jail for decades, or even life.

"But the limited-government stance is that if the government is going to do that to someone, they should have to clear a really high bar."

Gene Mills, head of the influential Louisiana Family Forum, also has come around, after much soul-searching. He told The Advocate on Tuesday that "we're very interested" in the issue but added that "it's not necessarily a traditional issue we would get involved in. We're trying to make sure we don't get caught in the mix of some unnecessary infighting."

By the end of the week, Mills had announced his support in his weekly newsletter, noting that he doesn't often agree with Morrell and quoting John Adams in explaining his decision.

The Family Forum and AFP both backed the criminal-justice reforms passed by the Legislature last year, helping to give cover to conservative lawmakers who might otherwise have faced political consequences from the effort.

In fact, this year, there's been a push to roll back some of those reforms, led by Rep. Sherman Mack, R-Albany, who chairs the House Committee on the Administration of Criminal Justice.

But Mack also has become a leading supporter of the unanimity requirement. He'll be the bill's lead sponsor on the House floor, Morrell said.

"We're trying to build a bipartisan group of people of different perspectives who all agree that (allowing split verdicts) is something we shouldn't do," Morrell said in an interview. "Someone like Sherman Mack is able to bring that to the fore -- that no matter how you come at this issue, people from very different perspectives all agree this is ridiculous."

Morrell noted that other prominent voices on the political right have rallied to the cause. Sen. Dan Claitor, R-Baton Rouge, eloquently decried the split-jury law as the Senate considered the bill. Claitor recounted how, as a young prosecutor, he "upcharged" some defendants -- charging them with more serious crimes -- just to take advantage of it. (Defendants accused of lesser felonies are tried before six-member juries, which must return unanimous verdicts.)

Also joining the fight is retired Air Force Col. Rob Maness, a tea party activist who has mounted several losing efforts for political office. In recent weeks, Maness has been heavily promoting Morrell's bill on Twitter.

"It's an interesting bill in that there are people who don't agree on anything who agree on this," Morrell said. "Even if we don't agree whether the sky is blue, whether you believe in small government or big government, we agree that no one should be able to take your liberty away without a unanimous vote."

While he's heartened by the support the bill has gotten on the right -- including unanimous passage by Mack's Republican-heavy committee -- Morrell said its fate in the House is hardly assured.

"I think it's going to be very close," he said.