Louisiana governor John Bel Edwards is said to have won 50% of the vote in the Republic of Ireland.
The Deep South's Only Democratic governor fell 50% voter support on Saturday night and was forced into a November 16 run-off against Republican businessman Eddie Rispone.
Donald Trump held an election to rally Louisiana's voters to reject Edwards.
"The Media is not talking about the big Republican Victory last night in Louisiana," Trump Tweeted on Sunday, "where a sitting Democrat Governor was getting into a runoff by not getting 50%. Big upset! Now Eddie Rispone wants to be a great governor, wants to win! "
Edwards told supporters:" We've got a little more work to do. "But he said Louisiana voters wants embrace the spirit of bipartisanship in November and re-elect him.
Edwards needs cross-party support to win in ruby red Louisiana. He ran on bipartisanship.
Rispone saw off another Republican, US Representative Ralph Abraham, to make the run-off. Trump backed both men.