“It’s just irresponsible,” said Mr. Wheeler, who is 58. “I’ve been in places where people are infected, I’ve been in hospitals — it’s just my reality right now. It is what it is.”

Officials in state after state have postponed in-person voting in the last month, grinding the Democratic primary to a halt as the impact of the coronavirus has disrupted every aspect of American life. However, in Wisconsin, pleas from state Democrats to delay voting were ignored by the Republican leaders in the Legislature, who said moving the election was too drastic a measure and an infringement on personal liberty.

Republicans in particular expressed outrage when the state’s Democratic governor, Tony Evers, proposed an expanded absentee ballot voting system that would mail a ballot to each of the state’s millions of registered voters. Republicans also successfully blocked an executive order by Mr. Evers on Monday to use emergency powers to delay the election, after the State Supreme Court, which is controlled by conservatives, reversed Mr. Evers’s order.

The consequence was an election on Tuesday that was criticized as both unsafe and illegitimate. National figures like Senator Bernie Sanders of Vermont called for it to be delayed, and the leaders of the Democratic Party of Wisconsin — which was seeking to win a vital State Supreme Court seat — said it could not encourage people to vote in good faith.

Erin Baldeon Fischer, a 32-year-old graduate student, said she saw the line at her Milwaukee polling place on Tuesday and decided the health risk might be too great.

“I have a 9-month-old; I’m not sure I feel comfortable being there with an infant at home,” she said. “I’m not sure it’s a responsible decision as a mother.”

Mary Corder, 70, usually votes in her senior assisted living facility, but decided she couldn’t vote in this election after the location was shut down. Ms. Corder said she found out her polling place was closed only yesterday, after voting there for years.