Pole winner Simpson led the 19-car field to the first corner of the 20-lap race, where he ran wide and flew high into the air over the bump on the exit.
Reece Gold inherited the lead, ahead of fellow Detroit GP race winner Siegel, Louis Foster and front-row starter Colin Kaminsky. Simpson recovered in sixth.
Foster passed Siegel for second on the opening lap and attacked leader Gold, who escaped a lock-up at Turn 6. Simpson and Kaminsky then clashed over fifth at Turn 13, after the latter had run wide at The Kink, with Kaminsky dropping to 14th after just avoiding the tirewall. Simpson later fell back to 10th after another sketchy moment.
Siegel repassed Foster at the start of lap five for second position, with Foster then coming under attack from Jacob Abel. Hunter McElrea moved up to fifth from 13th on the grid, while Rasmussen ran sixth, but had a big moment at Turn 5 trying to pass McElrea and badly locked up his left-front tire before sailing through the run-off.
Abel passed Foster for third at Turn 1 on lap six, while Siegel caught Gold at the front and passed with him with a great move around the outside of Turn 5.
At half distance, Siegel led Gold by 2.2s, ahead of Abel, Foster and McElrea. James Roe passed Rasmussen for sixth, as Simpson’s recovery embroiled him in a great battle with Ernie Francis Jr for eighth.
The race then went full-course yellow, as Rasmussen suffered a brutal crash into the concrete when his left-front tire, which he damaged earlier, appeared to delaminate just as he got to the curb. The erstwhile points leader walked away unhurt from his wrecked car.
At the restart with seven laps to go, Abel grabbed second from Gold on the run to Turn 1 and McElrea jumped ahead of both Foster and Gold at Turn 5. Gold and Foster then brushed wheels at Canada Corner, before Foster was given a blocking penalty, which forced him to give up fifth to Roe.
Siegel pulled out a 2s lead, and Abel chased him down with McElrea in tow, but the positions remained static to the flag – with Siegel taking over the championship lead. Gold held off Roe for fourth, ahead of an angry Foster, Danial Frost and Simpson.
Jamie Chadwick, who qualified inside the top 10, went off into the gravel at Turn 1 while battling for ninth with Josh Pierson and dropped to last. She recovered to finish 15th.
