Gov. Bobby Jindal let an open secret slip during an interview with a national media outlet this week: He and U.S. Sen. David Vitter aren’t exactly friends.

“If you turn (your recorder) off, I’ll tell you what I really think about him,” Jindal reportedly told the National Journal when asked about Vitter, who is running for governor this year.

Jindal, who is term-limited and weighing a run for president in 2016, has refused to endorse a candidate in this year’s gubernatorial primary, though several of his key advisers have been hired by one of Vitter’s rivals, Republican Public Service Commissioner Scott Angelle. Also in the race: Republican Lt. Gov. Jay Dardenne and Democratic state Rep. John Bel Edwards, of Amite.

Pearson Cross, a political scientist at the University of Louisiana at Lafayette, said the icy relationship between Jindal and Vitter has been known in Louisiana’s political circles for some time, but the fact that the governor acknowledged the reported rift is unusual.

“It just doesn’t sound like Bobby Jindal — not to a reporter, anyway. He has been so on-message,” Cross said. “It may be that David Vitter is getting to him a little bit. It is quite out of character for the governor who we’ve come to know over the past seven years.”

Jindal’s office didn’t respond to a request from The Advocate for comment on his relationship with Vitter or response to the National Journal article, which was topped with the grim headline: “Why Bobby Jindal and David Vitter Hate Each Other.”

In the article, Jindal traces his rocky relationship with Vitter back to 2010, when he wouldn’t endorse the incumbent U.S. senator for re-election.

“I made it very clear we wouldn’t endorse,” Jindal told the Journal. “I didn’t endorse the senator the last time he ran, and he was upset about that. He was publicly upset about that.”

Vitter has dismissed claims that he’s hurt over the 2010 snub, but he repeated what has become an oft-used apparent swipe at Jindal’s future political ambitions.

“As I’ve clearly said, this will be my last political job — elected or appointed — period,” Vitter said in a statement to The Advocate on Thursday. “I’m running for governor to confront Louisiana’s biggest challenges head-on, not to avoid them or play politics with them. I’m running to build a brighter future for Louisiana, and any previous races aren’t particularly important.”

Vitter has recently amped up criticism of Jindal and the looming state budget crisis, calling for a special session, if elected, to address the issue and clearly signaling he doesn’t trust Jindal will in his final months in office.

Cross said the rocky relationship between Vitter and Jindal stretches back before the 2010 election endorsement slight.

“The first sign of any kind of real problem here goes back to the moment when David Vitter had his crisis in 2007,” Cross said.

In 2007, Vitter admitted he had committed a “serious sin” after his phone number showed up on a Washington prostitution ring’s list of clients from several years earlier.

He asked for privacy and never directly addressed the scandal. Jindal, too, shied away from discussing it and cryptically told The Advocate in a 2008 article that Vitter would “have to answer to the voters.”

According to Cross, “Jindal said he was praying for his family, but he didn’t come out and say, ‘I support David Vitter; he’s a good man, and I’m sure this was a misstep,’ or anything like that. He really just didn’t want anything to do with it.”

Among issues widening the rift: The two have taken decidedly divergent positions in Louisiana GOP races. In 2011, they found themselves in a fight for opposing candidates, Cross said.

“There was a lot of vying at that point to see who was going to be ‘Mr. Republican’ in Louisiana,” Cross said. “After that, many people then said it looks like Vitter is a more powerful player even in state politics than Bobby Jindal is.”

Vitter also has been seen as instrumental in electing Bill Cassidy to the U.S. Senate and unseating longtime incumbent Democrat Mary Landrieu.

“You get the sense that (Vitter) regards Jindal as this sort-of junior player — someone who needs to be encouraged to be bold,” Cross said. “I think Bobby Jindal probably resents that a lot.”

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.