The book argues that prophylactic rules designed to limit temptations are not a backwater but a cornerstone of what is best in our country. In our modern prosecutorial culture, one might be tempted to think that white-collar bribery laws, which I categorized as “corrupt intent” laws, would be the appropriate tool for fighting corruption. But they are problematic. If a bribery statute is narrowly drawn (or interpreted), it covers only brazen, unsophisticated exchanges and does not actually solve problems of money being used to influence policy and undermine representative government. A narrow law will punish only clumsy politicians like William Jefferson, who hid his rolls of cash in a freezer.
Justice Alito has the same narrow view when he couldn't fathom corruption other than someone giving a politician or a public employee a wad of cash.
Using the First Amendment as the basis for the conservative justices' Citizen United decision is dubious at best, when no one was denying any group the opportunity to speak freely or the media to freely report the news, but under the context of elections, and the amount of money causing a shift of free speech and influence to only those with money.
No one gives money to a group because they like the group. They give money in hopes that they can gain influence to whomever or whatever that benefits themselves.
Corruption by definition draws on this concept of influence to gain advantage, and is sealed when the one being corrupted acts on his/her own benefit and the benefit of the one doing the corrupting, as opposed to acting in the best interest of whom or whatever the represent.