NEW YORK (Reuters) - Democratic presidential hopeful Elizabeth Warren is a champion of the corn-based ethanol industry when she campaigns in rural towns dotting the U.S. Farm Belt.

FILE PHOTO: Democratic presidential hopeful Sen. Bernie Sanders (D-VT) and his wife Jane Sanders wave as they march during the Independence Day Parade in Waukee, Iowa July 4, 2015. REUTERS/Scott Morgan

But in Washington, the U.S. senator from Massachusetts is among the co-sponsors of the Green New Deal, which calls for the end of all fuel-powered cars – and, thus, the end of the domestic ethanol industry.

The competing stances, shared by Democratic candidates including U.S. Senator Bernie Sanders, illustrate how the party’s growing orthodoxy on climate change often clashes with local political realities.

While environmental groups and progressives applaud Democrats’ calls for dramatic action to combat climate change, ethanol enjoys strong support in the Farm Belt, where agribusiness workers helped deliver the White House to President Donald Trump in 2016.

Biofuel groups have launched a campaign to persuade candidates on the benefits of ethanol and some candidates have changed or hardened their views, even though their environmental allies believe the fuel is harmful.

“There’s a disconnect between where we have seen leading Democratic contenders be in terms of support their corn ethanol and soy biodiesel and what we believe is the right thing to do for climate policy,” said Rose Garr, a campaign director at Mighty Earth, an environmental group headed by former Democratic California congressman Henry Waxman.

The group has been running an aggressive field campaign in Iowa. Activists are confronting candidates in front of video cameras, trying to convince them to abandon support for ethanol -- a longtime litmus test for winning the battleground state of Iowa, which holds the first presidential nominating contest.

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Iowa is the nation’s largest producer of ethanol, with the industry supporting 44 ethanol plants and more than 40,000 related jobs. Democrat Barack Obama won the state twice, and Trump won it in 2016, but the ethanol industry has grown frustrated with Trump.

The president’s trade war with China eliminated a key buyer of U.S. ethanol, and the administration has handed oil refineries a record number of exemptions to the nation’s biofuel laws.

This could provide an opening for Democrats. Senators Sanders and Kirsten Gillibrand, once foes of the biofuel mandate, have converted to ethanol boosters as they campaign in a field of more than 20 candidates for the 2020 nomination.

Like fellow senators Warren, Cory Booker and Amy Klobuchar, who all have publicly supported ethanol, they also are sponsors of the Green New Deal. Former Vice President Joe Biden has supported ethanol but also has an environmental plan that calls for phasing out of fuel-powered cars.

None of the campaigns responded to requests for comment.

Patty Judge, chairwoman of Focus on Rural America, noted that most Democratic climate change proposals call for a long phase-out of fuel-powered cars and said ethanol is currently the best alternative. Her group has organized more than a dozen trips to ethanol plants in Iowa for this cycle’s White House candidates to educate them.

“Ethanol is the cleanest renewable option we have today, and it’s absolutely the wrong answer that we abandon renewable fuels and go back to burning 100 percent fossil fuels,” Judge said.

But Scott Farber, a vice president at the Environmental Working Group, a Washington-based research and advocacy organization, said Democratic candidates cannot simultaneously support the Green New Deal and the U.S. Renewable Fuel Standard, the 2005 federal law that requires ethanol and other biofuels to be blended the nation’s fuel pool.

Ethanol is largely produced from corn. Environmental activists say it is not as clean a fuel as they once thought because blending it with gasoline continues U.S. reliance on fossil fuels and burning it still produces carbon dioxide.

“We can no longer afford to be burning fossil fuels or corn ethanol when there are far more environmentally transformational alternatives that address the climate crisis,” Farber said.