Reply #23: Two other reasons: 1/ LA has a Dem. governor and would be replaced by a Dem. if he had to resign.

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2/ Craig pleaded guilty to a crime, while Vitter did not and has not been charged and condemned, which allows them to keep him while claiming you are innocent until found guilty.

(Obviously, the homosexuality issue is probably there as well, but there may also be a political calculation that Vitter is a safe seat for a few more years for the GOP, while Craig can be replaced quickly by a GOPer who will become the incumbent in 08 for the next election).