IOWA CITY, Iowa — Kaleb Johnson rushed for 109 yards and three touchdowns, and backup quarterback Brendan Sullivan added another rushing touchdown as Iowa defeated Northwestern 40-14 on Saturday. The Hawkeyes (5-3, 3-2 Big Ten) scored 28 third-quarter points behind Johnson and Sullivan to take control. After leading 7-3 in the second quarter, the Wildcats allowed 37 straight points. Johnson, who is second in the nation in rushing, had a 26-yard touchdown run late in the first half to give the Hawkeyes a 12-7 halftime lead. He added a 41-yard touchdown run in the third that put Iowa up 33-7 and followed that with a 25-yard TD run later in the quarter. It was the sixth 100-yard rushing game of the season for Johnson, who has 16 rushing scores. Sullivan, who played in 13 games with eight starts in two seasons at Northwestern before transferring to Iowa last spring, entered the game with 9 minutes, 25 seconds left in the second quarter to replace starter Cade McNamara. Sullivan threw for 79 yards while rushing for 41 yards, including a 6-yard touchdown run that started the Hawkeyes’ third-quarter dominance. Kaden Wetjen added an 85-yard punt return for a touchdown for Iowa in the third quarter. Northwestern (3-5, 1-4) scored on an 85-yard interception return by Theran Johnson in the second quarter and a 72-yard punt return for a touchdown by Drew Wagner in the fourth quarter. The takeaway Northwestern: The Wildcats, who had just 163 yards of offense, came into the game ranked 129th nationally in total offense and 119th in scoring offense. Northwestern’s average starting field position was its 21, and after getting into Iowa territory on its opening drive didn’t cross midfield again until midway through the fourth quarter. Iowa: Sullivan’s entrance into the game brought some life to the Hawkeyes offense. His running ability showed up on a 40-yard pass to tight end Johnny Pascuzzi, when Sullivan raced downfield to throw a key block. The Hawkeyes defense, which struggled last week in a 32-20 loss at Michigan State, responded with its best effort of the season. Up next Northwestern: At Purdue on Saturday. Iowa: Hosts Wisconsin on Saturday.