The free market when applied to the public sector often causes significant problems. One of the reasons this should be a compensated position is because of who it attracts to serve the public. It's why I'm in favor of raising salaries for politicians at the state and local level as well. If you make it unpaid, chances are significantly higher that your applicants will be wealthy or some form of nepotism. Make it paid, open it up to anyone with the desire, and you're far more likely to get the best candidates. When it comes to public office, that should always be our goal.