The race many people are watching is between Democrats Jeff Barth and Matt Varilek.
One of the two men will receive the party's nomination to take on Congresswoman Kristi Noem for South Dakota's lone U.S. House seat this November.
Rather than do any campaigning on Tuesday, Barth prepared to host a block party at his house as results come in. It's another aspect of Barth's nontraditional campaign.
He's called out Noem, mainly on her participation at Agricultural Committee meetings, and he's debated with opponent Varliek on gay marriage, with Barth saying he would support it.
But Barth got the most attention for an internet video he posted a few weeks ago. In it, he took a comedic approach. Barth will find out if it worked later, as the votes are tallied.
Campaign supporters of Varilek, who is a former staffer of Sen. Tim Johnson, did take part in a last-minute push to get voters out to the polls. They worked into the evening making phone calls, encouraging others to vote for Varilek.
One area of the state that Varilek's campaign is watching closely is in Minnehaha County because of Barth's position on the county commission.
Secretary of State Jason Gant expects to start releasing results at 8 p.m. View the numbers on the KELOLAND.com Results page.