DES MOINES — Just before he stepped down from the podium, the entrepreneur Andrew Yang had a message for the crowd of Iowa progressives, to whom he’d touted a universal basic income and economic revitalization.

“The opposite of Donald Trump,” he shouted, “is an Asian man who likes math!”

Yang was one of a parade of lesser-known Democrats who tried out potential presidential campaign slogans and honed their personal brands at the annual Progress Iowa dinner Thursday in Des Moines, hoping to stake out a niche in what’s likely to be a historically massive field of Democrats running for president in 2020.

From Pete Buttigieg, the 36-year-old mayor of South Bend, Indiana, there was a promise of generational change delivered in red state–friendly language: “Freedom! Security! Democracy!”

Rep. Eric Swalwell, of California, spoke at length of his family’s humble Iowa roots, promising to “Go big, be bold, do good.” Sen. Jeff Merkley opened by reminding Iowans of his trip to the border during the height of child separation and his commitment to environmental justice. Yang talked about the looming threat of robot trucks.

Officially, only Yang was running for president. But unofficially, the dinner was one of the first proving grounds of the 2020 presidential campaign — and a preview of an onslaught of presidential hopefuls who will come to Iowa, home of the nation’s first presidential caucus, in the new year.

Merkley, who said he was edging toward a presidential run, called his possible 2020 campaign a “David and Goliath” venture. Buttigieg told BuzzFeed News a presidential run would be “very much an underdog project.”

But Merkley and his fellow speakers were all well aware of the possibility that a presidential campaign offered. “There are so many curious and unexpected things that can happen in the course of a campaign,” Merkley said. “Who knows how that will all unfold?”

As one attendee, a fan of Swalwell’s, put it: “It’s Iowa — so it could be anyone.”