UPDATE: Jay Dardenne crosses party lines, endorses Edwards; Louisiana GOP chair calls Dardenne ‘the Nick Saban of Louisiana politics’

Republican Jay Dardenne is expected to cross party lines and endorse Democrat John Bel Edwards in the Louisiana governor’s race Thursday morning, dealing a potentially significant blow to Republican U.S. Sen. David Vitter.

Edwards’ campaign had said Wednesday that it was planning to make a “major campaign announcement,” offering no other details. But multiple sources close to both Edwards and Dardenne confirmed to The Advocate that Dardenne plans to endorse Edwards during a news conference on LSU’s campus. None of the sources had been authorized to speak on the record.

Both Edwards and Vitter have spent the past week touting major endorsements in the race. On Wednesday, Vitter announced that he had won the backing of former Republican Gov. Mike Foster. Earlier this week, the Louisiana House Republican Delegation also endorsed Vitter’s campaign.

But Dardenne and Scott Angelle — the two key Republican gubernatorial candidates who didn’t make it into the runoff — had not yet come out in support of either candidate in the days since the Oct. 24 primary. Dardenne, in particular, had been said to be edging toward an endorsement in recent days, though.

Dardenne said late Wednesday, “I’ll be willing to talk tomorrow (Thursday).”

Vitter’s campaign didn’t immediately respond to a request for comment on Dardenne’s decision to endorse his Democratic rival.

Recent polls have shown Edwards with a double-digit lead over Vitter with two weeks left in the runoff.

Edwards won about 40 percent of the vote in the Oct. 24 primary, while Vitter came in second with 23 percent. Angelle won about 19 percent of the vote, and Dardenne took 15 percent.

The three Republicans had engaged in a bitter battle that flooded televisions with negative ads aimed at Angelle and Dardenne from pro-Vitter groups.

During one candidate forum, Dardenne was asked how he differs from Vitter he answered that he had never frequented prostitutes — a direct dig at Vitter’s 2007 prostitution scandal. Vitter admitted that he had committed a “very serious sin” after his phone number was found in the logs of the DC Madame.

A recent television ad from the anti-Vitter GumboPAC highlights remarks made by Dardenne and Angelle about Vitter during various debates, calling Vitter “vicious” and “Sen. Pinocchio.”

While the animosity has been palpable during the campaign cycle, the decision for Dardenne to endorse a Democrat in the race would come as a jolt to what’s already become an unusual campaign in Louisiana. Dardenne, a lifelong Republican and current lieutenant governor, handed out Barry Goldwater push cards with his mother as a child.

In his statement endorsing Vitter, former Gov. Foster does not take direct aim at Edwards. Rather, he sets his sights on the Democratic Party, in general.

“It’s either trying to give away hard-earned money of working people or trying to turn race against race, rich against poor, one group against the other,” Foster said. “The Democratic Party gaining control of Louisiana scares me.”

Republicans are securely in charge of both chambers of the Legislature and all the offices that are elected statewide.

But pollsters have said that a high-profile endorsement from a Republican in the race, could tip Edwards over the edge.

“It would be beneficial to the Edwards’ campaign because it gives permission in a matter of speaking for Republicans to vote for a Democrat,” pollster Verne Kennedy, of Market Research Insight, wrote in a recent analysis of the race.

Vitter, a two-term U.S. Senator, previously served in Congress and the state Legislature. He has never lost an election and had long been the presumed frontrunner in the governor’s race.

Edwards, who serves as chairman of the House Democratic Caucus, has been in the state Legislature since 2008.

Follow Elizabeth Crisp on Twitter @elizabethcrisp. For more coverage of Louisiana state government and politics, follow our Politics blog at http://blogs.theadvocate.com/politicsblog .