Yesterday I noted that Rep. Mike Castle, Republican from Delaware, may be interested in running for the Senate in 2010, giving the GOP a great shot at that seat — but leaving a very vulnerable House seat behind. You may see the inverse in Louisiana, where the lone Democrat in that state’s House delegation, Charlie Melancon, has confirmed that he is considering challenging U.S. senator David Vitter for reelection next year. John McCain carried Melancon’s district with 61 percent, and state representative Nickie Monica appears set to give Melancon a tough race if he seeks reelection to the House.