The hype about Minnesota's civic engagement is rooted in data: The state had the highest voter turnout rate in the country in 2012, a whopping 18 percentage points above the national average. The causes include higher-than-average educational attainment and income, as well as a long history of political activism and civic participation.

But, mirroring national trends, Minnesotans are more likely to stay home in years when there isn't a presidential race on the ballot. After more than three-fourths of Minnesotans voted in 2012, only about half voted in 2014, for instance. And those drop-offs have big ramifications.

Since President John F. Kennedy was elected in 1960, Minnesota voter turnout has been fairly consistent in presidential years, though turnout has dipped slightly since hitting a high of nearly 80 percent in 2004. Not seen on this chart: They have also been consistent in their support, backing Democrats for president every year since 1972.

Off-year turnout has been steadily declining in recent years. In 2002, nearly two-thirds of voters showed up, but at the off-year election in 2014, just half turned out.

Turnout matters greatly in determining the winner, especially in recent election cycles. This chart shows how the DFL wins when more of its voters show up -- which tends to be in presidential elections -- while the GOP fares well during off-years, when those DFL voters often stay home.

Each party has its own distinct dilemma: Republicans must figure out how to win over more voters in presidential years, while the DFL must get its voters to the polls in off years.