I agree, for the most part, that the less government power a political figure advocates, the less likely they are to become corrupted. Taken that way, it seems a libertarian politician is far less likely to become corrupt than a Green party politician, for all that I prefer the Green party’s platform.
More than any of that, though, is an unwillingness within all of the political parties to police themselves. Across the board, political groups are more than happy to point the finger at their opponents and intransigently unwilling to investigate, prosecute, and punish corruption within their own ranks. I suspect it’s because there is an endemic level of corruption throughout the entire two-party system, and those who might be willing to hold members of their own party to high ethical standards either have a few skeletons in the closet or simply aren’t trusted by the party hierarchy because they don’t have a few skeletons in the closet.
Any time a group holds power over a population, I see a reluctance among the rank and file members to hold those in power accountable for ethical breaches. Not just in politics, either. Police, doctors, and teachers often either collude to protect unfit members (because if we’re allowed to question those members, what will stop us from questioning all members?) or the system is set up to discourage reporting of wrong doing.
The only time I’ve ever seen a group of people who policed themselves internally to a higher degree than they were policed externally was the stories I heard from my mother, an RN, regarding the Board of Registered Nurses in Texas. They were absolutely ruthless, and it was far, far better for a nurse to self-report an error than it was to be reported by another nurse. Or worse, get caught trying to cover up a mistake. A self-reported error would get a warning and perhaps some remedial classes to cover whatever knowledge was lacking. A report by another would often get a suspension and mandatory retraining. Evidence of a cover up often led to revocation of the nursing license.
Now, mind you, that is anecdotal only, and probably fifteen to twenty years out of date. However, I suspect that if this were the case, it was primarily because women and the nursing profession had to work so hard to prove themselves, they were completely intolerant of anything threatening their standing.