Which way is the wind blowing on alternative energy? Look no further than Iowa, where turbines have shot up across the flat, open landscape in recent years. Nationally, wind energy is still a nascent industry, accounting for just 4.4 percent of overall electricity production last year. But Iowa made an early bet on wind, and it's proving that alternate forms of energy can take on coal—if the conditions are right. And this has put the Republican candidates for president in an awkward position as they campaign in the swing state.

Iowa has come a long way since 2007, when the region received less than six percent of its electricity from wind and 75 percent from coal. By 2013, however, wind accounted for 28 percent of its electrical grid, with coal dropping to 59 percent. And coal’s dominance will continue to diminish. Last week, the public utility Iowa Interstate Power and Light said it would shut down or stop burning coal at five of its power plants in the next few years.

All this is music to the ears of liberal environmentalists, of course, who have long championed alternate sources of energy. It's hardly surprising that, in the 2014 election cycle, Democratic candidates reaped 70 percent of federal contributions from the American Wind Energy Association.

But Republicans were actually among wind energy's early proponents. In the early 1990s, Iowa Senator Chuck Grassley was the lawmaker who authored the original legislation creating the wind production tax credit, the federal policy that’s been key to making wind competitive. President George H.W. Bush signed the tax credit into law in 1992, and George W. Bush renewed it. “I’m glad to defend the wind production tax credit and wind energy,” Grassley said in May. Among wind energy’s advantages, Grassley noted that it displaces “more expensive and more polluting sources of energy, lowering electricity prices for consumers.” Critics, he said, “disregard the many incentives and subsidies that exist for other sources of energy, and are permanent law.”

Today, though, GOP support for wind investment is scarce. Nearly all of the Republican candidates for president have come out against the wind production tax credit. At a summit in Iowa in March, former Florida Governor Jeb Bush said he wanted to phase out federal benefits for wind energy and renewable fuels like ethanol—another popular issue in Iowa. “Ultimately, whether it’s ethanol or any other alternative fuel, renewable or otherwise,” Bush said, “the markets are ultimately going to have to decide this.