The unanimous decision of the Iowa legislature to expand the state’s scholarship tax credit (STC) program yesterday once again demonstrates that school choice programs grow even more popular once implemented. Iowa’s STC expansion bill raises the credit cap from $8.75 million to $12 million and expands the types of corporations eligible to receive tax credits for donations to scholarship organizations. The bill adds no new regulations. Six of the seven states with STC programs enacted before 2010 have subsequently voted to expand those programs. The chart below shows the legislative support and opposition in four of those states. (The expansions in Indiana and Pennsylvania were part of legislation covering other issues so they were excluded from this analysis. The chart includes information for Arizona’s corporate‐​donor STC program but not its individual‐​donor STC program, for a similar reason.)

The most dramatic shift was in Georgia’s State House, which moved in just a few years from a fairly even divide to overwhelming support. Support in Iowa went from overwhelming to unanimous. While Florida’s Senate barely moved, support has grown considerably in the House. Arizona has also had modest increases in support for school choice in both chambers. A survey by Harvard University’s Program on Education Policy and Governance found that 72 percent of the American public already supports scholarship tax credit programs. The survey found even higher support among parents, African‐​Americans, Hispanics, and registered Independents and Democrats. There have not yet been any studies measuring whether support in a given state increases after enacting an STC program, but if legislative support is a reliable proxy then the answer appears to be in the affirmative.