I don’t care if you are a Republican, Democrat or something in between, if you are going to lead people, you have to lead by (good) example. If you can’t do that, then you shouldn’t lead. Period. Not paying income tax is leading by poor example and it should automatically disqualify someone from serving as a leader in government. There may be excuses, there may have been mistakes, it may be "complicated". Regardless, it distracts from the business of the public and worse, it creates a bad example. Finally, even if you make it through the confirmation process, you’ve got something hanging over your head, an example that can be pointed to by others to say, see here, you did it, and you got away with it. Why not me?
It shouldn’t even be a question. I appreciate folks like Governor Richardson and Nancy Killefer who bow out as soon as this issues arise, and thereby setting a good example of the right thing to do when you’ve done the wrong thing.