Be careful what you wish for. The problem with trying to undo Citizen's United is that it's often oversimplified as "corporations are people", but the decision was (to quote Wikipedia) "that it was unconstitutional to ban free speech through the limitation of independent communications by corporations, associations, and unions". Under those terms, that would include The New York Times, MSNBC, AARP, and the SEIU with regard to candidate and ballot measure endorsements.
$1B was spend in independent groups and $5B by the candidates and parties. By comparison, Americans spend $7B / year on potato chips.