NEW ORLEANS -- Incumbent Sen. David Vitter has easily won the Republican nomination and will face Democratic primary winner Rep. Charlie Melancon in a U.S. Senate race in Louisiana.

Vitter and Melancon each defeated two lesser-known candidates in their party primaries Saturday. With little competition in the contests, both Vitter and Melancon have already engaged in a war of attack ads.

Melancon has attacked Vitter for his involvement in a prostitution scandal. Vitter admitted in 2007 an unspecified "serious sin" after his phone number appeared in the records of a Washington prostitution ring.