The television station, which was the only local affiliate to carry the debate live, garnered the best Friday night ratings in at least 15 years and possibly ever, said KSTU marketing research director Melissa Freeman.
From 8:30 to 10:30 p.m., the station got a 12.6 rating, meaning 12.6 percent of 839,000 households in Utah were watching the debate that night.
Meanwhile, KUTV Channel 2 got a 7.8 rating; KSL Channel 5, 6.1; and KTVX Channel 4, 3.1.
Normally, KSTU earns a 3.4 rating on its Friday night schedule.
It runs "Bones" reruns in that time slot.