One of the oldest ethical/moral questions knocking around human civilization is "Does the end justify the means?" Or to put it another way, is it morally justifiable to commit a bad act to achieve a good result?
The answer that I was taught when I was young was no it is not. By commiting that bad act you taint the good. However, as I have gotten older, I've come to the conclusion that things are not necessarily that clear cut especially in the realm of modern American politics. Given how money driven it has become, I wonder if there is a candidate out there that can measure up to lofty goals. It seems to me that by the time the candidate reaches the national stage, they've become so reliant on Big Money and PAC's that they've compromised themselves (or prostituted themselves depending on how you look at it). They have to play to constituencies because that is where the money is and without money you don't have much a political career. Therefore they are perforce required to make "strange bedfellows" even when such combinations may be repugnant. to their followers.
It is not enough that we simply support good ethical candidates. I believe that we must also reform the system in which they operate in the following ways.
1.) Downplay or eliminate primary elections. This is where most of the candidate buying and selling goes on. This is also where a lot of the extremist politicos make their voices heard and have what I regard as undue influence.
2.) Let's have some serious campaign finance reform now. McCain-Feingold is a good step in the right direction but it doesn't go far enough.
3.) Let's get rid of a lot of these restrictive election laws that stifle the growth of third parties. AFAIC we really don't have a two party system  in this country but rather one party with two wings.
If we want principled people to run for office then we need to clean up the political enviroment.