Having taken the lead on lap 85, catching polesitter Power who had to slow trying to lap Romain Grosjean, Newgarden looked set to record a dominant double at Iowa, having been peerless on Saturday’s opener.
But suddenly on lap 235, a failure at the right-rear of the car sent Newgarden spinning hard into the wall, ending his race on the spot. The Team Penske driver was able to get out of the car and was unharmed but bemused by the crash.
The caution period sent everyone into the pits, and they emerged in the order of O’Ward, who jumped ahead of Power in a previous pitstop cycle, to lead the train from the Australian, Scott Dixon and Scott McLaughlin.
Green flag racing resumed on lap 250 after Newgarden’s crash, with McLaughlin moving past Dixon for third, while Jimmie Johnson engaged in a tussle to the finish for fifth place with IndyCar points leader Marcus Ericsson.
Over the final stint, O’Ward eked out his gap to Power, who was doing the same to McLaughlin and Dixon, which meant the gap between the frontrunners stretched out over the closing stages.
O’Ward crossed the line 4.25s ahead of Power, as McLaughlin completed the podium another 5.2s back. Chip Ganassi drivers secured a 4-5-6 finished with Johnson allowed to stay ahead of Ericsson, despite it causing the Indy 500 winner’s championship lead to shrink to eight points over Power.
Felix Rosenqvist also produced a late charge like his Arrow McLaren SP team-mate to take seventh place ahead of top rookie David Malukas.
Andretti’s Grosjean and Dale Coyne Racing with Rick Ware Racing’s Takuma Sato completed the top 10, with British rookie Callum Ilott a creditable 11th for Juncos Hollinger Racing ahead of Colton Herta for Andretti.
Defending IndyCar champion Alex Palou had a low-key race in 13th place, a lap down, as his recent dip in form continued for Chip Ganassi Racing.
IndyCar Iowa - Race 2 results