All the King's Men (1949)

Assigned to cover Stark's campaign, journalist Jack Burden asks his editor, "What's so special about him?" "They say he's an honest man," is the reply, and this puts him in the "man bites dog" category of newsworthiness. And he is an honest man, at first, motivated to study law and to run for office out of a genuine desire to fight corruption and abuse of power. But, as Lord Acton famously said, "power corrupts, and absolute power corrupts absolutely." In allowing himself to exploit the same mechanisms that he once protested, in a vain effort to use the ends to justify the means, Willie makes himself politically and spiritually vulnerable, and he does not have a trusted advisor or a moral foundation to keep him from spinning out of control.

It is interesting to watch the other characters decide how much corruption they are prepared to accept or participate in. Jack switches from being a journalist to what would now be called a specialist in "oppo" research (finding dirt on the opposing). A judge agrees to support Stark, swayed in part by the "good comes out of bad" argument, but probably swayed more by the chance to be Attorney General. Still, there is a limit, when he is forbidden to prosecute a crony of Stark's, when he must publicly oppose Stark. Even the prospect of blackmail will not force him to back down, only to kill himself.