Some sins are no doubt worse than others. Thankfully, our Heavenly Father has the capacity to forgive them all if true repentence is shown. He asks us to do the same.
And there's the sticking point, but I'll leave the forgiving up to God and Wendy Vitter.
But I wouldn't ever vote for this guy.
There is a difference between forgiving repentant sinners, and giving them the huge honor and respect of selecting them to be you leader. He could have stayed home and had a successful life and not put his family out on the line to e destroyed with the (true) news of his sins. That is the problem here.
One of my pet peeves is the pious Jimmy Carter type, who pops up like a mushroom after a terrorist outrage or spectacularly vicious crime, sermonizing to all the rest of us about our need to "forgive." You're treading dangerously close to that here.
Number one, forgiveness is a spiritual rather than temporal matter (Matthew 22:21). If a loved one were killed, I would try to find it in my heart, by God's grace, to forgive the perpetrator and not be destroyed by my hatred. But I would still want the civil authorities to punish him to the fullest extent of the law. There is even less need for talk of "forgiveness" in a non-criminal matter concerning the public trust.
Number two, forgiveness is only the prerogative of the one who has been wronged. Vitter didn't do anything to me. Only his wife and family can decide whether to forgive him. For me it is a purely practical rather than moral matter, as I mentioned in a prior post-- nothing more than I would consider if I were interviewing someone for a job. Vitter has displayed extremely poor judgment and a willingness to betray his most solemn vows. He has exposed himself (and by extension, the well-being of the citizenry whom he represents) to blackmail and extortion. He belongs OUT of office.
Number three, as you correctly note, there is no obligation to forgive unless true repentance is shown. Hanging on to an elected office is not the way to show true repentance. Someone with repentance in his heart, in my opinion, would have already resigned his position and not waited until being outed by the news media.
-ccm