A bombshell hidden-camera video released Wednesday airs a claim that Arkansas Sen. Mark Pryor has privately told gay rights activists he supports a redefinition of marriage to include gay and lesbians unions. Pryor, who is in a tight reelection battle, has publicly maintained an anti-gay-marriage stance in the red state in order to stay electable.

'I support traditional marriage, and I've been pretty clear on that for a long time,' Sen. Mark Pryor said in a May 31 news broadcast on KHBS-TV40 in the city of Fort Smith.

But one of the state's prominent gay rights leaders told an undercover investigator with Project Veritas Action, a conservative group known for its 'gotcha' videos, that Pryor has assured gay marriage advocates he's on their side.

'If you tell anyone I told you that, I'm gonna find you, and I'll kill you,' the activist, Bailey Rae Bibb, says in the video after confiding in the hidden camera-wearing covert operative.

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Bailey Bibb, who chairs the largest Young Democrats gay caucus group in Arkansas, said on a hidden camera that Sen. Mark Pryor has assured her he supports marriage equality for gays and lesbians

Bibb made it clear that she was telling the investigator, posing as the partner of a wealthy potential donor, something that wasn't common knowledge

NOT SO FAST: Pryor told an Arkansas TV news audience in May that ' I support traditional marriage, and I've been pretty clear on that for a long time'

Bibb leads the Stonewall Caucus of the Young Democrats of Arkansas. She spoke to a man posing as a gay man who said his wealthy partner was considering making a large donation to support Pryor's reelection effort.

'I'm having some misgivings about it, given his marriage stance,' he tells her.

Bibb replies while Pryor is 'not going to openly come out and say, "Oh yeah, I support it",'he changes his position 'if you ask him personally, just people-to-people.'

Asked if she has personally had that conversation with the senator, Bibb explains, 'Oh, yeah,' adding that Pryor had told her 'I'm not against' gay marriage equality and that he is 'not going to outlaw it.'

'He said to a small group, like, "Hey, you know, I’m not going to try to outlaw it, you know. I don’t think you should be discriminated against",' Bibb says on camera.

'No, he’s not a bad person.'

Bibb did not respond to phone, Facebook, SMS text and messages seeking comment. The Pryor campaign did not immediately respond to a request for clarification about the senator's position on gay marriage.

Pryor's main opponent, Republican Rep. Tom Cotton, has not wavered from his anti-gay-marriage position.

'I believe that marriage is between one man and one woman,' he told KHBS in May.

Cotton holds a 4.4 percentage-point lead in an average of recent polls, according to Real Clear Politics. Pryor's seat could be one of six the Republican Party needs to flip in order to cement control over both houses of Congress.

Pryor is one of only a few Democratic senators – Louisiana Sen. Mary Landrieu and West Viginia Sen. Joe Manchin are the others – who publicly oppose a wave of state laws validating the right of gays and lesbians to legally marry.

In red states, openly embracing a politically progressive position like marriage rights for gays and lesbians can spell doom for a Democratic candidate if Republicans make it the centerpiece of attack ads.

Democratic Arkansas Governor Mike Beebe has also said publicly that he opposes gay marriage.

Pryor spokesman Michael Teague told the Arkansas Democrat-Gazette last year that the senator had a 'moral belief that marriage is between a man and a woman,' and believed that homosexuality is a choice and not an inborn trait of biology.

Those positions are now ripe for speculation in the light of Wednesday's video exposé.

Bibb, the Democratic activist, confirmed in a follow-up phone call what Pryor had said privately

Pryor (right) and his main opponent, Republican Rep. Tom Cotton (left) debated Monday night, but the gay marriage issue wasn't raised

Project Veritas Action founder James O'Keefe told MailOnline that in Arkansas, 'key workers, donors, supporters and elected officials have an expectation that their Democratic Senate candidates are lying in order to gain votes and it doesn't bother them one bit.'

'We are talking about a casual disregard for the truth from the grassroots all the way to the top.'

His video includes a second admission from Paragould, Arkansas Mayor Mike Gaskill, that 'the sad thing about politics' in his home state is that 'people can't stand up and say what they really, really want to do and believe in.'

O'Keefe is known for his take-no-prisoners sneak attacks and over-the-top video dramatizations.

In one video this year, he staged a U.S. border infiltration by a man dressed in an Osama bin Laden costume, rolling video as the man waded across the Rio Grande from Mexico.

In another he demonstrated how an Ebola-infected jihadi from the ISIS terror army could motorboat across Lake Erie from Canada without a challenge, and stroll into the Rock and Roll Hall of Fame in Cleveland, Ohio.

But it's his political hit pieces that generate the most media attention.

In 2013 his operatives filmed wireless phone company employees passing out 'Obama phones,' free mobile phones paid for with U.S. tax dollars, to people who said they would sell them for drugs, shoes, handbags and spending cash.

Last week O'Keefe released a surreptitiously made video showing supporters and staffers of Kentucky Democratic Senate hopeful Alison Lundergan Grimes saying that she was playing a 'lying game' by publicly supporting her state's coal industry.

'You know she has to say that,' one campaign staffer says on tape, 'because in Kentucky if you don’t support the coal industry you are dead.'

Bailey Rae Bibb, chair of the Young Democrats of Arkansas Stonewall Caucus, is chummy with Arkansas Gov. Mike Beebe – another red-state Democrat who says publicly that he opposes marriage rights for gays

PRIDE: The Stonewall Caucus is a politically active gay and lesbian group within Young Democrats for Arkansas, and its energetic liberal campaigners have the ear of progressive pols throughout the state

Gay rights has had a pendulum-like trajectory in Arkansas, one that provides hints to Sen. Pryor's leanings.

Sodomy was illegal in Arkansas between its 1836 founding and the passage of a 1976 law decriminalizing it.

One year later Pryor's father, then-Governor David Pryor, signed a second bill once again making the practice illegal, following a widely publicized case of two men engaging in oral sex in a Pulaski County, Arkansas 'drunk tank' holding cell.

That law stood until 2002 when the Arkansas Supreme Court declared it unconstitutional. It was Sen. Pryor, then the state's attorney general, who made the decision to let the ruling stand and not appeal it to the U.S. Supreme Court.

But he later conceded that in 2004 he voted against a statewide ballot initiative banning gay marriage. That measure passed, but was overturned in May 2014 by a state circuit judge.

'My position on that specifically is well-documented,' he said in video footage released days later by the conservative America Rising PAC, an opposition research group.

'That was a ballot initiative here in Arkansas ... I voted for the amendment to ban gay marriage in Arkansas.'

As a senator, his recent record on gay rights has been a continuing study in U-turns.

In 2010 Pryor stunned Arkansans with a flip-flop on the repeal of the Pentagon's 'Don't Ask, Don't Tell' policy, a Bill Clinton-era directive that banned gay men and lesbians from serving openly in the military.

'On many previous occasions, I have said that I would oppose repeal,' he conceded, announcing his change of heart.

Pryor is the latest in a long string of left-leaning US political candidates stung by hard-charging conservative video provocateur James O'Keefe

Mike Gaskill, Democratic mayor of the northeast Arkansas town of Paragould, told O'Keefe's undercover cameraman that politicians often can't be candid about their beliefs when votes are on the line

But a 2012 Senate bill proposing to ban discrimination against gays in federal workplaces has yet to receive his endorsement, despite co-sponsorships from all 52 of his fellow Senate Democrats, plus two Republicans and both independents.

During the 2009-2010 congressional session, according to Project Vote Smart, Pryor enjoyed an 80 per cent positive rating from the Human Rights Campaign, America's most vocal gay rights policy group.

Two years later his rating fell to 70 per cent.

This year, as his electoral deadline approached, that rating stands at 60 per cent.

If Bailey Bibb, the Young Democrats of Arkansas activist, is right, Pryor may soon swing back toward full agreement.

'If Baily Bibb is telling the truth, then Mark Pryor is lying,' O'Keefe says in his video.

But for now, with Election Day less than three weeks away, the endangered Arkansas senator is sticking to his guns.