Problem: We have legislators and executives beholden to special interest groups and a desire for reelection.
Solution: Congresspeople, the president and vice president and members of the cabinet should be forced to put up 10% of their net worth at the beginning of each term. At the end of each term, they would receive back:
Half of the amount they put up multiplied by the nation's approval rating for the branch of government they're in (Legislature or Executive branch)
Half of the amount they put up multiplied by the nation's (not their district's) approval rating for their own performance.
~45% of what they put up. This is a baseline constant so that a 55% approval rating - roughly an average performance - means they get most of it back.
This would force legislators to think about the benefit to the nation of the policies they're supporting, instead of the benefit to their own re-election. Because it's based on % of net worth, it doesn't disadvantage poorer government officials signficantly.
Even better, you could reduce the baseline constant to incur a cost to taking political office, so that people aren't as tempted to take political office just for personal gain and power, but instead are forced into a degree of altruism - a sorely lacking trait in many (though not all) politicians these days.
You could also adjust the baseline constant for presidents to account for the fact that presidents tend to have declining approval ratings over time (excluding Clinton, whose approval rating increased).
Although even great officials rarely go above 70 or 80%, and even truly horrible officials rarely drop below 20 or 30% (call this the blind ideologue condition), if you make the percentage of net worth high enough, this doesn't matter (I assume 10% is high enough... make it 20% if you have to).
Admittedly, the problem with this is that approval rating is only a rough proxy for how well a leader is doing. Truman ended his term with approval ratings in the 20s, while he's now seen as a good president. If you don't like approval rating as an indicator, you can try and create some other form of report card. WHATEVER it is will be better than now.