The Theory of Political Selection
Considering Congress as a marketplace fails to apprehend the reality of corruption. Campaign contributions in exchange for legislation frames lawmaking as a marketplace, where consenting actors cooperate for mutual gain. But this isn't what's really going on. Naturally, the conception of Congress as a place to strike deals between the wealthy and the powerful would be bad enough, even if it was true. But its worse than even that.
Customarily, government holds the monopoly on the use of coercive force. This license is used in order to exert selective pressure on business, to insure that abusive commercial and industrial practices are eliminated. But the reality is not just different - its the opposite. Because politicians simply cannot run for office without wealth, but must skillfully avoid being caught appearing to have been influenced by money (something that contributors also have an interest in, since a corrupt-looking politician doesn't serve them either), they must come to running for office already convinced of the positions that wealthy contributors favor. Otherwise, they are simply not sponsored.
Politicians don't coercively regulate wealth; wealth coercively regulates politicians.
Money doesn't change a politician's mind; it simply pre-determines who may run for and win office. It's not adaptation - it's natural selection.