Waves of grain and grain and grain … they’re not kidding about Iowa. You leave a city and, as the decayed edge recedes, the yards of discarded cars and abandoned half-collapsed motels, boarded-up strip malls, the corn comes forward, even, swaying, planted to the soft shoulder of the road. You’re used to it in Australia, but there, planted fields are interrupted by dead land, dry river beds, grazing land. None of that here. The state is one big farm, planted from Illinois to Nebraska, with small cities rising from it.

They call it prairie, and now people imagine it was always like this, but of course no land is like this, round-up ready and prepared for the harvesters. This has been planed flat by agribusiness, which runs the joint, corn, once for the great cities of the plains, then for export, then for the corn syrup that goes into every food, puffing Americans up like the Skywhale, killing their pancreases. Ethanol too, for a while, before the oil boom hit, and you’ll find no politician with national ambition who doesn’t have a detailed position on biofuel subsidies.

Iowa, a state white as Homepride, having parlayed its geographical centrality into political power, first in the nation in primary season. Iowans have got accustomed to having had met the man who has the nuclear codes, two years earlier, at a party in a garage. Whether by cause or effect, the state has come to be dead centre, politically. One of the few states to have WYSIWYG districting — three of its four districts are competitive, two of them genuinely so — it has, this year, a Senate competition on a knife-edge, with every poll in the last few weeks falling within the margin of error. Proud pioneers, Iowans see themselves as frontier democrats, a people who made the agrarian civilisation the founders had in mind for the new country; they made a new Rome by clearing the land and staking their claim. Jesus, and don’t they let you know it, in the politics.

“I’m the daughter of a farmer, I grew up one of nine children, I became a doctor and went into the military,” Republican Senate candidate Joni Ernst told a packed hall at St Ambrose university in Davenport, at the border, the very edge of the grain. Severe, businessy, with  helmet-like fringe and a ramrod military bearing. She also told them “becoming a doctor in the military wasn’t easy when you were a child of a poor farmer, one of nine”, and in conclusion, “I wasn’t stopped from becoming a military doctor by being one of nine children of a farmer, growing up in poverty”.

In between, she spoke of the minimum wage — she’s against, wants better jobs — Obamacare — she’s against it but doesn’t want repeal — the Environmental Protection Agency, and federal environmental standards — she’s ag-… you’re way ahead of me — and dealt with her Democrat opponent, Bruce Braley, whom she was trying to skewer as an Obama clone. “He voted with his party 90% of the time!” she thundered. It’s a harsh insult in American politics, to accuse you of subscribing to a political philosophy and sticking to it, thick and thin.

Braley pauses, gathers himself, to defend progressive politics, and responds forcefully. “My grandfather cleared a farm here, he died on it, he was buried on it.” Jesus. Son of the soil, flowing into our veins, into the waters of life, into the corn syrup. Neat, blue-suited, moon-faced, a former four-term congressman, Braley has none of Ernst’s cred. He looked like he’d been hatched in a DC pod. So he’d played it quiet for most of the debate, letting a few challenges to his competence, patriotism and masculinity slide across the plate. But he let rip at the end, having kept his dead granddad as an ace in the, erm, hole for last. Whether he won or not, he could hardly be accused of an excess of rhetoric and symbolism.

Strange sort of depressurisation at the centre, like the tornadoes that sometimes come through this way. For months, pundits of all sides have said that if there is any chance of the Democrats holding the Senate, it will come down to Iowa. That presumes a few certain and near-certain losses — Montana, Louisiana, West Virginia — and one or two Democratic wins from the Republicans, to even things up. A week ago that prospect looked gone, with the GOP heading for a 53-47 victory. But in South Dakota and Kansas, independents are giving the Republicans a run for their money, and in Alaska, the hapless Democrat incumbent is hanging on to the amazement of all.

By the time Ernst and Braley squared off, Iowa was back in play, and, after an undercard event for the local congressional district, where Democrat Dave Loebsack (“Loebsack — he’s a bag of dicks” slogan not used by anyone, unaccountably) was seeing off a perpetual challenger Mariannette Miller-Meeks (doctor.veteran.problem solver.), a dozen or so foreign press flooded into the media room. The MC thanked local dignitaries, the local TV station, whose blue-blazered news director had last been seen setting out pizzas in the kitchen. Outside, team Braley, 40 or 50 strong, could be faintly heard, banging their signs, cheering Bra-lee Bra-lee — purple signs, I’d noted, coming in, Braley running hard, away from his party. There was no GOP cheer team. A Republican woman in a spangly red hat had watched me watching the display, sidled up and said “See — big government in action”. The vast machinery of the republic, balancing on a pin.

But of course, this wasn’t the main game. Around the small meetings and candidates debates a vast TV war is swirling. The big money has come to Iowa, with the notorious Koch brothers and others pouring in millions — $40 million of soft money so far, from about 50 different groups, seven-eighths of them right-wing, and the Democrats struggling to match them. The ads are wall-to-wall, those directed against Ernst almost wholly focused on her commitment to cutting state income tax, ending abortion, and other Tea Partyesque themes. “Jodi Ernst, too extreme.” Its a simple message, one used to great effect by Harry Reid, Senate majority leader, who faced a Tea Party challenge from Sharron Angle in Nevada in 2010. No one thought Reid would win, but he did, and saved the Democrats senate majority that time. That debacle convinced the GOP that they had to wind up the Tea Party. The Tea Party had other ideas, and it took until the GOP primaries this year to thoroughly root them out. Ernst is acceptable to the Tea Party, but she’s also a respectable Republican, not an angry no-tax nutjob like Angle, and so the “extreme” tag might not work so well.

Meanwhile, the ads directed against Braley are eye-wateringly harsh, little 30-second spots using stills and voiceovers that latch onto something like missing some military intelligence briefings and conclude: “Braley — a traitor to our country and a despicable human being” — sotto voce “paid for by Frontier Spirit/Americans for Prosperity/Crossroads GPS” or any one of myriad other groups, all energised by the Supreme Court Citizens United decision, allowing for unlimited “soft” money.

With the Islamic State and Ebola crises erupting just as the midterms began, the Kochs and their ilk have had plenty of material to work with. The election has come to be dominated by phantom terrors derived from real but manageable risks. Yet for the Tea Party and the Republican right there is no sense of carnivale as there was in 2010, no sense that the election of Barack Obama is an aberration, soon to be reversed. Now there is only a hard slog to save some terrain.

The Right are dealing with a world they understand less and less, as demonstrated by the one killer point Braley gets Ernst on — skewering for a full 30 seconds on his refusal to commit to renewable energy subsidies. “That’s thousands of jobs for Iowans, something farmers support, and she’s just being ideological.” And Ernst outclassed, and for Braley, a new ad being cut, amber waves of grain, and a row of wind turbines behind, going out to a heartland that isn’t entirely sure of itself anymore.