Action Sports with Leigh Roche

This story is part of an ongoing POLITICO series on how national policy issues are affecting the 2014 midterm elections.

CEDAR RAPIDS, Iowa — Rep. Bruce Braley is betting the farm on corn — and Democrats’ hold on the Senate may be in danger if he’s wrong.

The Iowan is touting federal support for ethanol while competing in one of 2014’s most critical Senate contests — and he’s banking on his ability to champion his state’s cause in D.C., where the corn industry’s political power has waned. While critics ranging from environmentalists to anti-subsidy fiscal conservatives have turned against ethanol, Braley is busy posing at gas stations that sell the corn-based biofuel, campaigning with farmers and pressuring EPA to protect the federal mandate that guarantees corn’s role in the U.S. fuel supply.

(Also on POLITICO: Cantor's final days)

His Republican opponent, state Sen. Joni Ernst, has been more elusive on the issue — saying she “philosophically” opposes government meddling in markets but promising to protect EPA’s ethanol program until all other subsidies are repealed. That sounds like waffling to Braley supporters, an impression Ernst has tried to counteract with some pro-ethanol rhetoric this week.

Less-than-overwhelming enthusiasm for EPA’s ethanol mandate is a rare stance for any candidate in Iowa, from either party, so a perception that Ernst is wobbly on biofuels would offer an advantage to Braley. Ernst’s opponents have also attacked her for planning to attend a Washington fundraiser hosted by the oil industry, one of ethanol’s biggest opponents.

But Braley, whose campaign leans heavily on his influence in Washington, faces pressure to show he can deliver. A key test is expected in the coming weeks, when EPA announces a decision that could make or break the federal mandate that requires gasoline refiners to blend ethanol into their fuel.

People in the home-grown industry agree that ethanol looms large here, though many are still deciding where they think Ernst stands.

(Also on POLITICO: Obama to GOP: Stop hating)

“I think renewable fuels can be a big issue in the race,” said Monte Shaw, executive director of the Iowa Renewable Fuels Association. Shaw, who lost a Republican House primary in Iowa earlier this year, says about 10,000 households in the state are directly invested in or employed by the renewable fuels industry, and nearly 300,000 Iowans are “pretty much directly engaged in agriculture,” he said. “That’s a lot of voters.”

“If you can’t find a senator in Iowa that supports ethanol, you’ve got a serious problem,” said Pam Johnson, a sixth-generation farmer in northern Iowa and chairwoman of the corn board at the National Corn Growers Association.

Braley expects Iowa voters to pay close attention to the candidates’ stances on the ethanol program, known as the Renewable Fuel Standard.

“There’s a clear choice,” Braley said in an interview after giving a campaign speech at a gas station in Marion, just outside Cedar Rapids — filled, like many gas stations here, with high-ethanol blends not usually found inside the Beltway. “My opponent, she is philosophically opposed to the Renewable Fuel Standard. I have been a strong supporter since I was elected to Congress.”

(Also on POLITICO: Roberts' foe begins to close gap)

Ernst, meanwhile, insists she’d defend the program too — while sticking to her tea-party opposition to the government interfering in business.

“While I do not believe the government should pick winners and losers in our economy, and from a philosophical standpoint I do not believe in taxpayer subsidies, I do believe that if we were to end subsidies, it would have to be done across the board, for every sector at the exact same time — meaning until and unless that day comes, I will passionately stand in defense of RFS and other related programs,” Ernst said in response to written questions from POLITICO.

Ernst has also tried other ways to burnish her agricultural cred, including boasting of her experience castrating hogs.

Adding to the drama is the fact that EPA is way behind schedule in making its decision on the ethanol program, which was legally due last November and was later expected to come in June.

The agency says it makes such decisions based on the merits, not politics. But whatever the cause of the delay, many observers note that the ruling has been pushed into a crucial stretch of the political calendar.

“That’s got to be on the minds of the White House,” said Eric Washburn, an attorney with the firm Bracewell & Giuliani who represents refiners and environmentalists opposed to the mandate. “And frankly, Iowa is one of the very few states where people actually vote on biofuels policy.”

The politics of corn

Obama carried Iowa by almost 6 points in 2012, and Braley had a clear lead just a few months ago in the race to replace retiring Democratic Sen. Tom Harkin. But the congressman has stumbled with some self-inflicted gaffes, including dismissing beloved Republican Sen. Chuck Grassley as “a farmer from Iowa who doesn’t have a law degree” — a videotaped statement now airing on a veritable loop in Iowa television ads. Lately, Braley has reshuffled his campaign staff while watching the race tighten to a toss-up in the polls.

At the same time, Iowa’s corn-based fuel seems to have lost much of its political heft in Washington, despite the state’s continued draw for presidential hopefuls.

Corn was on an upswing in 2005, when Congress created the mandate, and in 2007, when lawmakers expanded it to its current form, with the expectation that EPA would make refiners use ever-growing amounts of ethanol every year. Back then, oil imports were soaring, gasoline demand was expected to continue to grow, and supporters saw ethanol as a tool for reducing the United States’ reliance on the Middle East while curbing greenhouse gases.

But since then, the North American energy boom has cut the need for Mideast oil, and some green groups have vocally abandoned their support for corn...