[classicman]

The argument is that he made a vow to remain faithful to his wife, and he broke that vow, knowingly and repeatedly.
He also made a vow to serve the people of NY, honestly and to the best of his ability. Now we are left to wonder whether he considers remaining true to the latter vow.
Further, one of the main things we look for in an elected official is good judgement. When to exercise caution, when to take a risk, etc. He has shown monumentally poor judgement in his private life, which raises questions regarding his judgement in other areas.