Democrat Kirsten Engel is up by 8 percentage points over incumbent Republican U.S. Juan Ciscomani in their rematch in Arizona's Congressional District 6.
Engel has 53% of the vote to Ciscomani's 45%, with about 49% of the ballots counted so far.
Engel's lead shrunk slightly as some Cochise County results came in after 10 p.m. in the swing district, which includes voters in several counties including Pima and Pinal.
Ciscomani narrowly defeated Engel for the U.S. House seat two years ago. He was an aide to Republican former Gov. Doug Ducey.
Engel is a University of Arizona law professor and a former state legislator.