STORM LAKE, Iowa — Sen. Elizabeth Warren (Mass.) talked about drowned livestock. Sen. Amy Klobuchar (Minn.) delved into soybean prices. Former congressman John Delaney (Md.) bemoaned the privatization of Medicaid, and Julián Castro, an Obama Cabinet member, insisted that he is “very proud of the story of Storm Lake.”

In other words: The wooing of voters in Iowa, which will host the first caucuses of the 2020 presidential campaign, has begun.

This weekend, four Democratic presidential candidates and Rep. Tim Ryan (Ohio), who is considering a run, spent a bright but blustery day at the Heartland Forum at Buena Vista University. Much of the race has been dominated by national issues such as Medicare-for-all and the Green New Deal environmental plan. This event focused on more local concerns.

“They realize that this election is going to be decided this time in the Midwest,” said Art Cullen, the Pulitzer Prize-winning editor of the Storm Lake Times’s editorial page, who moderated the forum.

Jane Kleeb, chair of Nebraska’s Democratic Party, said party activists in rural states have been clamoring for more focus on rural voters.

“We want to see somebody running for president that knows what it’s like to be on a farm and have major industrial agriculture surrounding you, trying to squeeze you out of the market,” she said.

Candidates largely used the forum to highlight their ideas for rural America, a theme that many here say Democrat Hillary Clinton missed in her 2016 campaign.

A key issue that many addressed was how consolidation in the agriculture industry has caused higher prices and fewer choices for small farmers.

Warren said that she would appoint regulators to unwind mergers like the recent Bayer-Monsanto deal, which combined two major seed suppliers. “Twenty years ago, 600 different outfits were selling seeds. Today, basically, it’s six,” she said. “That means less to compete on price and, the diversity goes away that farmers want.”

Klobuchar also decried monopoly control of farming. She invoked the Granger Movement of the late 1800s, in which farmers and other activists successfully fought railroad monopolies.

“Literally this movement started where farmers were there with their pitchforks,” she said. “That’s what we need to see today.”

She also touted a $1 trillion infrastructure plan that would use tax subsidies, loan guarantees and federal money to help local governments repair bridges, roads and water systems while bringing Internet access to remote areas.

Delaney, who was a businessman before he entered politics, didn’t discuss breaking up specific companies. But he agreed that mergers can pose a problem.

“All the big companies have effectively controlled the part of the agricultural market where there’s no risk, and they leave the farmers in the one part of the market where there’s risk,” he told reporters after speaking at the forum. “What we’ve got to do is start updating these laws.”

Other topics came straight from the front pages of the local papers, which on Saturday reported that UnitedHealthcare is pulling out of the state’s Medicaid program, which will force more than 425,000 Iowans to change plans.

Delaney, who has spent much of his campaign in Iowa, criticized the state’s decision in 2016 to allow private companies to help manage the program.

Iowa “shouldn’t have privatized the Medicaid system,” he said. “That was a bad decision, and it was a bad outcome, and it hurt citizens.”

Warren and Klobuchar spoke about devastating floods this month that may have caused about $1.6 billion in damages.

But neither said how they would vote Monday on a major disaster relief plan that Republicans say would include some money for Iowa. Democrats say the bill lacks sufficient funding for Puerto Rico, which was devastated by Hurricane Maria in 2017.

Only a few questions were about trade, even though the Trump administration’s dispute with China has had a major effect on corn and soybean sales.

Klobuchar applauded the administration for putting aside $12 billion to help farmers affected by the trade war, but she said it’s not a complete solution.

“That’s not actually the same as selling things, right?” she said. “That’s not the same as having value with your product.”

David Weigel contributed to this report.