Corruption is a human tendency and will never not be a problem. Even with anti-corruption policies in place, without proactive measures to continually undermine corruption efforts, those policies attenuate across time. This is due to people figuring out how to circumvent the current rules of law or a degradation in integrity when following the the rule of law.

Once anti-corruption institutions put in-place to investigate and prosecute corruption themselves become corrupted, then the system will rapidly degrade to cover up the favored de facto political power corruption. Depending on the system in place, this can occur either top-down or bottom-up. In the US, it appears to be occurring top-down.

Political party loyalism always leads to corruption, which is why it's absolutely critical to have a multiple party system with strong de jure political powers to keep the de facto political power in-check. There are numerous historical accounts depicting what happens when you do not. In the US, both parties should be split up and serve as more representative components to their constituencies, and to keep each other in balance more so than what's transpiring today.