In 1984, Tom Harkin upset a republican incumbent to join Charles Grassley in the U.S. Senate.
Sen. Harkin has called it a career, paving the way for Iowa’s first new senator in 30 years.
The polls to choose the Republican nominee close across the state at 9 p.m. The results will finalize the general election ballot.
Rep. Bruce Braley (D) was Senator Harkin's pick to replace him. The Congressman ran unopposed for the democratic nomination.
On the republican side it's a five-way fight.
The list of candidates includes a talk radio host, a soldier, an energy executive, a car salesman and a prosecutor.
Throughout the GOP primary campaign, it has been anyone's race.
Most recent polls have Joni Ernst in front, followed by Mark Jacobs and Matt Whitaker.
Tonight we'll find out just how accurate those polls are.
Check back here for the Senate primary results as they come in.