Minnesota and Wisconsin share much more than bone-chilling winters: German and Northern European roots; farming; and, until recently, a populist progressive tradition stretching back a century to Wisconsin’s Fighting Bob La Follette and the birth of Minnesota’s Democratic-Farmer-Labor Party.

But in 2010 these cousin states diverged. By doing so they began a natural experiment that compares the agendas of modern progressivism and the new right. Wisconsin elected Republicans to majorities in the Legislature and selected a bold and vigorous Republican governor, Scott Walker. Minnesotans elected one of the most progressive candidates for governor in the country, Mark Dayton of the Democratic-Farmer-Labor Party.

A month after Mr. Walker’s inauguration in January 2011, he catapulted himself to the front ranks of national conservative leaders with attacks on the collective bargaining rights of Civil Service unions and sharp reductions in taxes and spending. Once Mr. Dayton teamed up with a Democratic Legislature in 2012, Minnesota adopted some of the most progressive policies in the country.

Minnesota raised taxes by $2.1 billion, the largest increase in recent state history. Democrats introduced the fourth highest income tax bracket in the country and targeted the top 1 percent of earners to pay 62 percent of the new taxes, according […]