With 100 percent of the vote counted, Charles Boustany Jr. leads Jeff Landry 45 percent to 30 percent, The Hill reported Wednesday.
Both men currently serve in the House, but Landry, who was backed by the Tea Party, decided to compete in Boustany's district after his district was eliminated by redistricting.
Democrat Ron Richard spoiled both men's victory parties, splitting their votes to come in third with 22 percent, The (New Orleans) Times-Picayune reported.
Richard had raised only $53,000 in his campaign while Boustany pulled in nearly $3 million and Landry $1.8 million.
Rounding out the race were a third Republican, Bryan Barrilleaux, and Libertarian candidate Jim Stark. Neither of them raised enough money to be listed on the website for the Center for Responsible Politics' OpenSecrets.org.
The runoff will be held Dec. 8.