Taxes
I wonder how much smaller the deficit would be if only we could get politicians to pay the right amount in taxes (before they get nominated for cabinet posts). You gotta figure the IRS bills of the ones who actually face confirmation are just a drop in the bucket, compared to all the officials who "forget" to pay taxes on their nannies, their gifts, etc..

At the same time, the tax code is not exactly confidence-building in its clarity. It can be complicated enough for an honest person to have trouble sometimes figuring out exactly how much they are supposed to pay. In the hands of dishonest people - or even just cagey opportunists - it's practically an invitation to cheat.

But when you're a high profile politician there are just a few standard ethics-related things you know you have to avoid if you want to keep your job: 1) don't cheat on your wife; 2) don't drink and drive; and 3) watch out for gifts: don't accept ones you're not supposed to, and pay taxes on the others. Most of us don't routinely think of the tax implications of gifts we receive. These guys do. It's one of only 3 things they have to worry about.