Ryan was expected to defeat Nehlen, but the contest was expected to provide a gauge of GOP presidential nominee Donald Trump’s effect on other Republican races.
Nehlen has frequently praised Trump during the campaign and Trump returned the compliment last week on social media, setting off a flap over whether the nominee would endorse Ryan.
Professor Mordecai Lee of the University of Wisconsin- Milwaukee said the controversy may linger.
“So that even though Trump, last Friday in Wisconsin, gave a formal endorsement to Paul Ryan, it would still be correct to interpret the degree of votes that Nehlen gets as kind of a Trump vote,” said Lee.
Nehlen says he agrees with Trump on many immigration and trade issues while Ryan has criticized some of the presidential nominee’s remarks.
The Wisconsin primary also features a Democratic contest between U.S. Senate candidates Russ Feingold, and Scott Harbach. Feingold is expected to win Tuesday and hopes to unseat Republican incumbent Ron Johnson this fall.