Rep. Charlie Melancon (D-La.) raised more than $500,000 for his challenge to Sen. David Vitter (R-La.), his campaign announced Thursday. Melancon now has some $2.26 million banked, about half the amount of the Republican incumbent.

"Our campaign is in a strong position to spread Charlie's message of ending politics-as-usual in Washington and bringing a more common-sense, bipartisan approach to the Senate that focuses on putting Louisiana first," Bradley Beychok, Melancon's campaign manager, said in a statement.

Vitter announced last week he raised some $1 million in the first quarter to bring his cash on hand to $5 million.