I believe most people go to politics with genuine intentions to make things better. Then they face a situation in which they either have to sacrifice their ethics and win, or keep their ethics and lose. Guess which ones eventually prevail.
I'm from a post-communist country, and I've seen many former dissidents, who clearly had stellar ethics (often they were made to suffer for publicly opposing communism), who got into power after the revolution and their behaviour became more and more ethically questionable over time.
I believe most people go to politics with genuine intentions to make things better. Then they face a situation in which they either have to sacrifice their ethics and win, or keep their ethics and lose. Guess which ones eventually prevail.
I'm from a post-communist country, and I've seen many former dissidents, who clearly had stellar ethics (often they were made to suffer for publicly opposing communism), who got into power after the revolution and their behaviour became more and more ethically questionable over time.