Sen. David Vitter, R-La., probably thought, or at least hoped, that his sex scandal was largely behind him. We learned last year, of course, that Vitter had used the services of the “D.C. Madam” — including making arrangements for liaisons while casting votes in Congress — despite being married and running on a conservative “family values” platform.

Vitter’s story reemerged a bit a month ago, in light of Eliot Spitzer’s prostitution scandal and the various similarities between the two controversies.

However, with the statute of limitations having expired, Vitter probably thought this humiliation was largely behind him. It’s not.

Defending herself against a sortie of felony charges stemming from running an alleged interstate prostitution business, Deborah Jeane Palfrey has subpoenaed Sen. David Vitter, R-La., to testify. Vitter’s telephone number appeared in the phone records of Palfrey’s business for February 2001, which Palfrey had released to the media. At the time that was revealed, Vitter issued a statement confirming he had used the service. Through his lawyer, Vitter has said he will not testify.

Late on Friday, according to the Legal Times, a lawyer who has represented Vitter urged a federal court judge to nullify the subpoena. The judge didn’t buy it.

For his part, Vitter, when asked about this by the New Orleans Times-Picayune, said, “I want to reaffirm how sorry I am to have hurt the people I love so deeply, starting with my family and certainly including the people of Louisiana.”

If he’s forced to testify, I suspect we’ll be hearing that apology again.

As for the broader political implications, how upset do you suppose the Republican establishment would be if a conservative Republican senator were forced to testify in a prostitution case in an election year?