U.S. Rep. Steve Scalise, the third-highest-ranking Republican in the House of Representatives, threw his support behind U.S. Sen. David Vitter’s gubernatorial campaign Monday.

Scalise praised Vitter as a hard worker willing to “take on special interests in Baton Rouge” as he made his endorsement.

“We’re going to need somebody that’s not only a bold fighter, but a bold reformer,” said Scalise, who holds the same Metairie-based seat that Vitter held when he was in the House.

Vitter also picked up the endorsement of former Republican U.S. Rep. Bob Livingston, whom he replaced in 1999.

Vitter is running against Lt. Gov. Jay Dardenne and Public Service Commissioner Scott Angelle, both Republicans, and Democratic state Rep. John Bel Edwards.

Scalise’s endorsement is a change for two men who — although both conservative Republicans — spent their early careers in the state House at odds. When Scalise had just started his term as a state legislator, he was put forward by anti-Vitter forces as part of a successful effort to force Vitter off the powerful Appropriations Committee.

After Livingston’s resignation from the U.S. House, Scalise flirted with the idea of running in a crowded field to replace him. After he decided to sit out that race, Scalise endorsed former Gov. David Treen for the seat, which Vitter ended up winning.

The relationship between the two men has warmed in recent years. The chief of staff in Scalise’s office as House majority whip not only served as Vitter’s top aide while he was in the House, but is married to his current chief of staff.

“David’s proven a lot of people wrong over the years,” Scalise said when asked about the history between the two on Monday.

“If you look at David’s work ethic, no one outworks David Vitter,” he continued, adding that Vitter’s ability to “focus in and get the job done” has been a key element of his success.

Vitter has already locked up a sizable portion of the state’s congressional delegation.

Republican U.S. Reps. John Fleming, Charles Boustany and Ralph Abraham have endorsed him, as has U.S. Sen. Bill Cassidy, whose successful campaign last year had significant help from Vitter and his staff.

The other two members of Louisiana’s congressional delegation — U.S. Reps. Garret Graves, R-Baton Rouge, and Cedric Richmond, D-New Orleans — have yet to make endorsements.

Follow Jeff Adelson on Twitter, @jadelson.