Last year Ms. Burke became active in the political wing of the United Automobile Workers union. She concluded the president was anti-worker. “What I really realize now, and didn’t before, is if he had his way, my God, our children would be working right alongside of us and none of us would be making any money, there would be no union,” she said.

“From what I was paying attention to and where I was getting my information,” Ms. Burke recalled of 2016, “I was not informing myself well at all.”

Neil Shaffer, the chairman of the Republican Party in Howard County, said he saw no signs of a “Trump revolt.” He predicted the general election would turn on the tone of the two major candidates, in a county where many voters have weak partisan identity and dislike divisiveness. “I think honestly this election will have more to do with personalities than with issues," he said.

Ms. Hubka is not optimistic the county will swing back to the Democrats in November. If she can shave 10 points off Mr. Trump’s 2016 margin, that would be a victory, she said. “I think it’s going to be a horrible, nasty election,” she said.

Even though she favors Mr. Buttigieg, she welcomes all of the organizers staying under her roof. “One of these three people’s candidates is going to be the nominee,” she said.

Usually after dinner, her three lodgers head upstairs to separate rooms to log data from their day or work the phones. “They call until 9, which I’ve advised against because Iowans don’t like to be called after 8,” Ms. Hubka said.