State Sen. Joni Ernst (R-Iowa) and Rep. Bruce Braley (D-Iowa) won their respective party's nominations in the race to succeed retiring Sen. Tom Harkin (D-Iowa), the Associated Press reports.
The race between the two candidates is considered one of the country's top-tier match-ups, as it could determine control of the Senate.
Braley leads Ernst by five percentage points, according to HuffPost Pollster.
The Huffington Post's Amanda Terkel and Samantha Lachman took a look at the race earlier this week:
In recent weeks, state Sen. Joni Ernst has taken the lead in the polls in the crowded GOP primary to replace Sen. Tom Harkin (D-Iowa). She gained national prominence after an ad entitled "Squeal," in which she talked about castrating pigs. Both Sen. Marco Rubio (R-Fla.) and former GOP presidential nominee Mitt Romney have backed Ernst, while Texas Gov. Rick Perry (R) is backing former District Attorney Matt Whitaker (R). Santorum, who ran against Perry and Romney in 2012, is backing radio host Sam Clovis. But Ernst's closest rival, according to recent polling, is businessman Mark Jacobs, the former CEO of Houston-based energy company Reliant Energy. As The Huffington Post has reported, Jacobs made more than $34 million there while the company suffered major losses and at times avoided paying federal income taxes. The winner of the GOP primary will face Rep. Bruce Braley (D-Iowa), who was criticized in April for making comments that were seen as insulting to farmers.