(I just got another idea for a game: surveys for pairs of characters. This needs to happen.)
Well, I still have ten years before I'm even old enough to run, and I'll probably wait until I'm at least forty to actually run at all, so I have no idea what will have changed by then. Ideally, I'd like educational reform to be one of my highest priorities, so possibly something to do with that, or possibly civil rights and other social policy things (which I'm sure would be important to my campaign, since I'll probably end up running as someone with a chance of becoming the first openly gay president). The literal first thing I'd do if I was elected would be to collapse into a chair and let it all sink in before sharing in the celebration and getting ready to make my speech, but that's obviously not the real question.
Oh God, I don't know. There are so many amazing pieces out there, both ones that I've played and ones that I haven't, that I'd never be able to narrow it down to one. Maybe it's just because I don't like picking favorites of anything (except color, for some reason). I do love pieces with large emotional ranges, or at the very least one very strong emotion so that it can be paired with a contrasting piece.
[Um, I know I need to do a lot more research on violin music as I write this, so the evasive answer is more me than him.]