Democrat Lauren Arthur, a state representative, led Republican Kevin Corlew, also a state representative, by more than 20 points with over 80% of precincts reporting in a district that backed both Trump in 2016 and Mitt Romney in 2012.
The district has gone Democratic before. Jason Kander won it by 11 points during his failed 2016 Senate bid.
The swing is significant given the seat's previous representative -- Republican Ryan Silvey -- who won re-election in 2016 by 20 percentage points.