For the reasons that TAPPED's Paul Waldman discussed earlier today, it's rather remarkable that the constitutionality of Arizona's campaign-finance law is even in question. Actual restrictions on campaign spending present a difficult question, as First Amendment values are put in conflict with democratic equality. Regimes like Arizona's, on the other hand, do not have the same tension. Candidates can spend as much money as they want, but candidates without the same resources are given the resources to compete.
Unfortunately, it looks as if Paul's predictions about what the Court will do were also correct:
Justice Anthony M. Kennedy, who definitely seems to hold the deciding vote on the newest test of the Supreme Court’s skepticism about campaign finance laws, made repeated comments on Monday suggesting that he is very wary of Arizona’s attempt to offset the impact of wealthy candidates paying their own way. Among a variety that could be noted, no remark was more telling than what seemed almost to be a rhetorical question: “Do you think it would be a fair characterization of this law to say that its purpose and its effect are to produce less speech in political campaigns?”
Kennedy is showing his hand in more than one way here. The only way that this law could be seen as producing "less speech" in political campaigns is if you assume that people with more resources inherently have more to contribute to public discourse. Otherwise, it's pretty obvious that public financing enhances free speech by broadening access to public office to more people, including those who represent non-wealthy interests. What we have here is a conservative majority that is actively hostile to the civic equality that democracy requires and is willing to make highly dubious First Amendment arguments to impose their values on the states.