I’m out of town at the moment, so I will have to let this passage from the NYT article summarize the relevant issue for me:
To William Maurer, the lawyer opposing the Arizona mechanism, whenever “a privately financed candidate speaks above a certain amount, the government creates real penalties for them to have engaged in unfettered political expression.” That “speaks” was not a slip, but a reinforcement of the money-equals-speech notion.
The fundamental problem, he said, is “the government turning my speech into the vehicle by which my entire political message is undercut,” because the public funds triggered are a penalty that reduces the impact of the privately financed candidate’s spending and speech. Chief Justice John Roberts Jr. made clear in the argument that he, too, sees triggered matching public funds as a limit on the privately financed candidate’s speech.
I am simply incapable of wrapping my mind around this interpretation of the First Amendment. To see the world this way, you literally have to have your brain screwed in backwards.