It's been a strange trip. Four years ago, who would've thought Biden might win Iowa?

Nearly a year ago, at the side of a snowy and windswept county road in north-west Iowa, I climbed the steps on to the “No Malarkey” campaign bus. Joe Biden rose to greet me. “Where have I been? In South Carolina, that’s where!”

We had seen all the candidates but him – Pete Buttigieg was practically a nextdoor neighbor. The week before, we had asked in a headline in our little country paper: “Where’s Joe?”

Donald Trump had been impeached and was being tried in the Senate. The Iowa caucuses were a few weeks off. Former Iowa governor Tom Vilsack, agriculture secretary in the Obama administration, rode shotgun while Biden held forth for a half-hour on fighting climate change through regenerative farming practices.

“It all starts here. We can do anything if we put our minds to it,” Biden declared.

And it all ends here. The former vice-president held a parking lot rally in Des Moines on the Friday before election day, his final call in a state he had worked since 1988 on his route to the White House but never quite won.

Related: 'It's all fake': Trump's manufacturing jobs promises ring hollow in midwest

When the February caucuses cleared, Biden was down in the pack. Buttigieg and Bernie Sanders were tied for first in a delayed result from a failed cellphone reporting app that may well have doomed Iowa’s half-century run as first-in-the-nation. Nevada is itching for pole position.

Iowa’s role was to winnow the field. Biden nearly was winnowed here and, a week later, in New Hampshire. Essentially, a half-dozen Democrats had their tickets punched out of Iowa from a field of 25. Mike Bloomberg had his own strategy, bypassing the first states with his bet on Super Tuesday. He could not bypass Elizabeth Warren, who ripped him to shreds in one of the final debates.

And Biden had done his work in South Carolina.

There, black voters rose up to have their say: No gambling on a lefty. They wanted Safe Joe to bring it home. Representative Jim Clyburn, dean of South Carolina politics, touched Biden’s shoulder. That was that. Little did I know, that blustery day on the bus, how it would play out.

Nor do I know this weekend before the election how this long, strange trip of the last four years will end.

Iowa is in play after Trump won the state by nine percentage points in 2016. The 2018 midterms saw two women, Cindy Axne and Abby Finkenauer, defeat two incumbent Republican congressmen. Senator Joni Ernst, a Republican who did a brain meld with Trump in her first term, watched her popularity tank – from over 60% to underwater. Ernst narrowly trails Democrat Theresa Greenfield in most polls. Democrats swamped her in fundraising. Biden holds a slight lead over Trump, who can’t afford TV ads in Iowa.

Next door, in Wisconsin, Biden has a healthy margin. Trump thinks he can take Minnesota, but it appears he is down by double digits. It’s grim for the president in Michigan, as well. The upper midwest has figured out that trade wars and picking fights with your friends can suck the life out of agriculture and manufacturing. Iowa and Wisconsin are among the most export-sensitive states in the nation.

And, as people honked in their cars in the Des Moines parking lot listening to Biden over their FM radios, Iowa set a weekly record for Covid hospitalizations. It’s as bad in Wisconsin, which Biden also hit on Friday along with Minnesota. Despite the danger, people are lining up for early voting from north to south, masked up and resolute for what surely will be a record turnout.

In my corner of Iowa, our county auditor expects a smooth and safe election with results by 10pm. Iowa is your early swing-state bellwether. If Trump loses Iowa or Ohio, he loses the presidency. Each is currently a dead heat. Who would have thought that four years ago – or even two years ago, when candidate John Delaney first crossed our threshold by helping shovel snow from our front door after a blizzard?

We’re worn out from the countless cafe campaign appearances, and rancorous debates, and this damned pandemic, and the stream of lies from a corrupter in chief. A record number turned out for the primaries – in Storm Lake, young Latinos caucused for Sanders in droves. They protested in the park for Black Lives last summer, and the police knelt right along. On Labor Day there was a big boat parade for Trump. His flags fly along those blacktops where the Biden bus ran. $60bn in trade and disaster subsidies to agriculture washed over those fields the past two years. We were wiped out by floods in 2019 and a freak wind storm in 2020 while California and Colorado burned.

We take note and vote. It all comes down to a few states like Iowa and Wisconsin, where Biden aims to seal that victory at long last.

• Art Cullen is editor of the Storm Lake Times in north-west Iowa, where he won the Pulitzer prize for editorial writing. He is a Guardian US columnist and author of the book Storm Lake: Change, Resilience, and Hope from America’s Heartland