Envision Racing's Nick Cassidy claimed his third Formula E win of the season in Portland, Oregon, on Saturday while Avalanche Andretti's Jake Dennis took second for the overall lead in the electric series.
Briton Dennis leads New Zealander Cassidy by a point after a strange 'peloton-style' race full of slipstreaming and overtaking, with cars running up to five abreast.
Porsche's previous championship leader, Pascal Wehrlein, finished eighth and dropped to third overall with four races remaining.
Another Porsche driver, Antonio Felix da Costa, completed the podium.
The top 17 cars were split by only seven seconds after 32 laps and 403 passes recorded through the field, with positions changing from corner to corner and the safety car deployed twice.
Cassidy started 10th at Portland International Raceway, being used by Formula E for the first time, and first took the lead on lap three in a battle with da Costa that he settled four laps from the finish.
"I’ve had a good run in America the last couple of years. I love racing here," Cassidy said.
Dennis, who found pole of less benefit than usual on a wider track, moved to the top of the standings after passing da Costa on the final lap for second place.
"There are some guys fighting for the championship and other guys with nothing to lose. A race like today is all about risk," the Briton said after his third successive second place.
"Me and Nick are really fighting for the championship. It’s just who takes the most risk. Some of those moves on Antonio were brave and he did a really good job there."
New Zealander Mitch Evans celebrated his 29th birthday by racing from 20th on the grid to fourth for Jaguar and also posted the fastest lap.
Both DS Penske cars had to start from the pit lane as punishment for installing a Radio Frequency Identification (RFID) scanner at the pit entry in practice, resulting in the team being fined a record 25 000 euros.
DS Penske driver Jean-Eric Vergne denied the scanner was collecting live tyre data.
"We merely read the serial number of the tyres in order for us to know what tyres are being used by others. Something any team can do (and surely does) by taking photos," he said on Instagram, adding that they did tyre pressure, temperatures "or anything else".
Rome is next on the schedule with a double-header of races over July 15-16 before the final two races in London two weeks later.
Reuters