John Kennedy speaking Friday at a rally in Baton Rouge, where President-elect Donald Trump spoke in support of Kennedy. (Drew Angerer/Getty Images)

John N. Kennedy of Louisiana has prevailed in the final U.S. Senate contest of 2016, beating out Democrat Foster Campbell for the seat being vacated by David Vitter (R).

Shortly after the polls closed, the Associated Press projected Kennedy the winner.

Kennedy, the state’s Republican treasurer, had endorsements from President-elect Donald Trump and Vice President-elect Mike Pence.

Trump won Louisiana by a wide margin during the general election last month and stumped for Kennedy on Friday during a visit to Baton Rouge.

Campbell, a public service commissioner, had faced an uphill climb in his campaign to defy polls that heavily favored Kennedy and Louisiana’s deeply red history. With the Democrat’s defeat, Republicans will hold a 52-to-48 edge in the Senate when Trump assumes the presidency next month.

Kennedy had more than 63 percent of the vote with 3,391 of 3,904 precincts reporting, in results posted on the website of the state Secretary of State’s Office.

Campbell conceded the race in a speech to his supporters Saturday in Baton Rouge, Reuters reported, with his Republican opponent leading. Campbell said he called Kennedy to congratulate him.

The Senate race in Louisiana was the last in the country because of a primary system that allows all the candidates, regardless of their party affiliation, to compete against one another on the November election date. The two front-runners then proceed to a runoff election in the following weeks. Last month, Kennedy and Campbell bested a 24-candidate field that included David Duke (R), a onetime Ku Klux Klan grand wizard, to advance to the final election Saturday.

In Louisiana, Republicans control all statewide elected offices as well as both chambers of the state legislature. The governorship is the only outlier.

Last year, John Bel Edwards (D) beat out Vitter, who faced continued scrutiny from a prostitution scandal. After losing the gubernatorial race, Vitter chose not to run for a third Senate term this year.

Despite working in government for the past quarter-century, Kennedy has billed himself as a Washington outsider.

“The swamp in Washington, D.C., has to be drained,” he said in a recent TV ad. “I can help. After all, we know a thing or two about swamps in Louisiana.”

Voters also filled two open U.S. House seats Saturday, choosing Republican Clay Higgins, a former sheriff’s captain known as the “Cajun John Wayne,” in the 3rd District representing southwest and south central Louisiana, and Republican state Rep. Mike Johnson in the 4th District covering northwest Louisiana.

Tyler Bridges contributed to this report.