Editor's Note: There are just 36 days until Election Day, and the NBC News political unit each day will profile the most competitive races this midterm season.
This seat – vacated by retiring Republican Tom Latham – has been in the political news since the springtime for its unpredictable GOP primary in June. State Sen. Brad Zaun won the most votes on primary day, but didn’t reach the 35% threshold needed to keep the race from going to a state convention. At that special nominating convention, the more than 500 delegates picked someone else – former Sen. Chuck Grassley chief of staff David Young – for the slot instead. A frustrated Zaun threatened an independent bid – which could have sunk Young’s chances – but he later dropped the idea. Young now faces Democrat Staci Appel, a former state senator, in a race both sides say is a top contest to watch.