Sure, you're up against "the purpose of a system is what it does". I'm sure many mainstream politicians actually earnestly care about individual liberty and reigning in corpos - it helps them sell themselves to the public. But the net effect is that when the dollars come calling, enough set aside those ideals to make the corpo agenda happen.

Without making some compromises and taking the money they would be replaced by someone who would.

They (well, all of us whatever we do, but some more then others) operate in an imperfect system.