People who think food needs to be higher on the national agenda should do a better job connecting the dots, said Bob Kerrey, the former governor and United States Democratic senator from Nebraska.

“You need to start off by understanding that agriculture is primarily a manufacturing business and make food an economic issue, rather than labeling it as a health or environmental issue,” he said. “Then you have to walk across the gulf between that and the people who are actually buying the food.”

But to many voters, food is not that complicated. “Politicians are intimidated by it, but voters aren’t,” said Celinda Lake, a Democratic pollster and political strategist. Last fall, she joined the Republican public opinion researcher Christine Matthews to study how food issues play out with voters. The bipartisan poll was commissioned by Food Policy Action, the HEAL Food Alliance and the Union of Concerned Scientists, the groups behind the barbecue party featuring Mr. Colicchio as part of the Plate of the Union campaign.

To draw attention to the cause, organizers recruited Larry Robinson, who sells rum cake and jambalaya out of his food truck in Miami. His truck, rebranded with the Plate of the Union logo, traveled to both conventions and will pop up in a dozen more cities before the election.

“I’m not here for the politics,” said Mr. Robinson, who has family members with diabetes. “We need kids to get healthier food.”