SINCE THE late 1990s, candidates for state office in Arizona have had two options: privately finance their campaigns or accept only public funds, subject to a cap. Candidates who opt in to the public system receive an initial lump sum, which is drawn from taxpayer funds, court assessments and voluntary donations. These candidates then receive additional funds if their privately funded opponents exceed a specified spending limit; expenditures by independent groups that support privately funded candidates may also trigger increased funds to those who accept only public dollars.

Critics contend this system is perverse. Candidates who rely only on private funds know that the more they raise or spend, the more their publicly funded opponents gain in the way of taxpayer dollars. This reality, critics contend, forces privately funded candidates and the groups that support them to think twice before fully exercising their First Amendment rights, lest they prompt a government move that bolsters their competitors and serves to advance political points of view with which they disagree. Several individuals and independent groups in Arizona have challenged the law’s constitutionality in a case that will be heard by the Supreme Court on Monday.

Detractors make some valid points, particularly when it comes to the fairness of the provision on independent expenditures. Why should independent expenditures that favor a privately funded candidate essentially be used against that candidate by triggering an increase in public funding for the competitor?

Still, the law’s core should be upheld, in no small part because the provisions in question were enacted in pursuit of the legitimate and compelling interests of reducing the corrupting influences of big money and special interests of all sorts. Privately financed candidates are permitted to raise as much money as they are able and are not restricted in how much of their own money they may use; publicly financed candidates, on the other hand, are subject to a cap on how much they may receive from the government, meaning that they could be outspent by a wealthy, self-financed candidate or one who is a prodigious fundraiser. Candidates rejecting public funds may also accept money from political action committees and political parties. Do privately funded candidates hesitate before surpassing the spending limit that triggers additional funds to a competitor? No doubt, but this is a strategic decision and not an exercise of government censorship or coercion.

If anything, the Arizona law encourages speech — a point made lucidly in an amicus brief written by former Reagan solicitor general Charles Fried on behalf of a bipartisan group of former lawmakers that includes onetime Republican senators Nancy Landon Kassebaum and Alan Simpson and former Democratic senators Bill Bradley and Sam Nunn. “By providing a voluntary public financing system for candidates that is viable,” the brief concludes, “the [Arizona] program aims to increase the speech in Arizona’s public discourse, enriching the marketplace of ideas.”