Conor Daly replaced Jack Harvey at Dale Coyne Racing for the second race as the Brit’s neck and back injuries were too much for him.
McLaughlin got away well, maintaining the lead over Palou. Kyle Kirkwood move up three spots to find himself in 9th, with Newgarden up to P10 from 14th.
Juncos Hollinger’s Romain Grosjean also had a brilliant start, vaulting up to 11th from 16th when the green flag was thrown.
AJ Foyt’s Santino Ferrucci quickly moved himself up to P15, including a brave pass on Rinus VeeKay.
McLaughlin, Palou, Dixon, Herta, Rosenqvist, Rossi, O’Ward, Rahal, Kirkwood and Newgarden was the top 10 from the end of the first lap all the way through to 92. Will Power was running in 19th after starting down in P22.
Conor Daly pitted from P24 on lap 86, but it was a slow one as the right front tyre was not fitted correctly.
The pit stop cycle saw Alex Palou take the lead as he brilliantly extended on fuel, jumping Scott McLaughlin for the lead as he was allowed to put before a yellow was thrown.
A caution was thrown on lap 101 as Agustin Canapino spun on pit exit. As Will Power had not pitted, he did so when the pit lane opened. As the cars on track were going slowly, the Australian gained 17 spots to move into P2.
Palou led Power, McLaughlin, Dixon, Herta, O’Ward, Rahal, Rossi, Rosenqvist and Newgarden was the top 10 on the restart.
Ferrucci continued to gain spots, passing the Meyer Shank Racing duo, Newgarden and Grosjean to move into the top 10.
Kirkwood and Ferrucci went at it for a couple of laps, going by side-by-side, with some rubbing included. The Andretti man held on, and he eventually passed Rahal for P8.
It was an early end to the day for Daly as he retired in the pits with an engine issue on lap 149.
Palou led Power, McLaughlin, Dixon, Herta, O’Ward, Rossi, Kirkwood, Rahal and Ferrucci with 75 laps to go.
Inside the top 15, Felix Rosenqvist’s day was done with just over 60 laps to go a scary failure on the right rear forced him to pit. The team confirmed it was a damper issue.
Race leader Palou boxed on lap 205, with Power coming in a tour later. A superb stop by Team Penske allowed the Australian to jump the Spaniard.
Power led from Palou, McLaughlin, Dixon, Herta, O’Ward, Rossi, Newgarden, Rahal and Kirkwood following the final round of stops. Newgarden moved up four spots through the pit cycle.
The 5-time Iowa race winner continued to make progress, passing Rossi for 7th with 5 laps left.
Despite lots of traffic, Power fended off Palou to take his 43rd career victory and first at Iowa, keeping him right in the mix for the championship. Scott McLaughlin completed the top 3. Dixon, Herta and O’Ward rounded out the top 6 as all the title contenders scored well.
On the last lap, there was a big accident involving Kirkwood, Carpenter, Robb and Rossi.
Sting Ray Robb hit the Arrow McLaren and got airborne as Rossi looked to be slowing, flipping over multiple times. Carpenter and Kirkwood crashed as they look to avoid the wreckage ahead, with the ECR driver’s left rear tyre landing on the aeroscreen of the Andretti.
