Even among the most engaged voters, the race for state superintendent may not attract much attention. But it is attracting huge amounts of money: upward of $43 million, mostly funneled to outside groups running advertisements in the race. The battle for the state school’s chief is between two Democrats: Tony Thurmond, a state assemblyman from the Bay Area, and Marshall Tuck, a former education executive from Los Angeles. The state superintendent, a nonpartisan office, does not have any independent policymaking authority, making the costly race even more peculiar. But charter school supporters have thrown millions behind Mr. Tuck, while the state teachers’ unions have given their dollars to attract votes for Mr. Thurmond. We spoke to Julie Marsh, a professor of education policy at the University of Southern California, to understand the significance of a race between candidates who agree on many major education issues, including more state funding for schools. Here is our interview, which has been condensed.