Antonio Felix da Costa made it back-to-back wins at Portland - and three Formula E victories in a row - while the 2024 title fight was blown wide open as points leader Nick Cassidy failed to score for a second day in a row.
In what was an excellent second race of the Portland weekend for Porsche, da Costa's fourth victory of the season - which have all come in the last five races - was backed up by team-mate and title hopeful Pascal Wehrlein grinding out a fourth-place finish despite running without a front wing for more than two-thirds of the 27-lap race.
Though there were the anticipated wild swaps of position throughout the order in the opening laps, second-place starter da Costa was one of a handful of drivers who spent the majority of the race at the head of the order along with eventual runner-up Robin Frijns and polesitter Jean-Eric Vergne.
Envision driver Frijns was the leader when the safety car - deployed so debris from multiple collisions could be cleared - came in at the end of lap 20, but da Costa dived swiftly for the lead as the field headed for the Turn 1/2 chicane on the restart.
Da Costa was initially hesitant to break away, with Porsche also asking him to "just stay ahead" of Frijns "if necessary" in order to keep Wehrlein, who'd lost his wing by running clumsily into the back of Edoardo Mortara, in the fight at the front of the field.
But as energy saving gave way into a flat-out sprint to the finish, Porsche - which still harbours hopes of catching Jaguar in the teams' championship - allowed da Costa to break clear of Mitch Evans, telling da Costa: "We will not risk the race win. Stay in front."
Frijns got back ahead of Evans for second at the start of the penultimate lap and hunted da Costa down gamely but ran out of laps to pass the Porsche, instead having to settle for a second podium finish of the weekend, a repeat of the 1-2 in Saturday's first race.
Da Costa's victory moves him up to fourth in the drivers' standings, 33 points off Cassidy, leaving him with an outside shot at what would be an unlikely second Formula E title.
Evans - who lost his win in Saturday's first race when he picked up a five-second penalty for hitting Jake Hughes - had been a permanent fixture in the top 10 and was up to fifth at the time of the restart, but was forced to put on a late charge as taking his second attack mode activation dropped him to eighth in the order.
Third place leaves him joint second in the points with Wehrlein, who fought hard in the closing laps to cling onto fourth ahead of Vergne.
Evans and Wehrlein are now just 12 points behind Evans's Jaguar team-mate in the drivers' title race, as Cassidy was compromised by the pack bunching up into the Turn 1/2 switchback.
Having been hit from behind, Cassidy's Jaguar was forced into the back of Jake Dennis, which left his front wing drooping down on the left-hand side and forced him to pit so it could be repaired.
The safety car that Cassidy had craved - he said on the Jaguar team radio "it's people's lives at stake here" in reference to the debris littered across the track - might have saved him, but the sprint finish left him with little opportunity to utilise an energy advantage and he ended up in 14th.
Jaguar still leads the teams' title race but its advantage there has been reduced to 33 points with 94 still available at the London season finale in July.
Nico Mueller backed up his fifth-place finish on Saturday with sixth in race two for the Abt Cupra.
Norman Nato was seventh ahead of Max Guenther (Maserati), while Envision driver Sebastien Buemi and Nato's Andretti team-mate Dennis both did what Cassidy couldn't by recovering into the points from visits to the pitlane.
Buemi had been part of the lead group in the race's early stages and even led for a while but was served with a drivethrough penalty for a technical infraction, while Dennis limped back to the pits with a right-rear puncture on the same lap as Cassidy - almost certainly the result of their clash (for which neither driver was to blame).
Both McLaren drivers ran encouragingly towards the front of the pack at the start but the team's race turned into a disaster.
Sam Bird had his race ruined when the front wing that had got stuck under Wehrlein's Porsche was spat out and collected by the McLaren driver, who was sent off onto the grass.
He tumbled to the back of the order where he remained until retiring in the middle of the race.
As he returned to the pits at the end of lap 11, team-mate Jake Hughes lost half of his front wing in a melee at the first corners in which he was hit by Nissan's Sacha Fenestraz - who earned a five-second penalty.
Hughes had a subsequent spin at the looping Turn 6 left-hander and retired late on.
Mahindra also fought at the front in the opening stages but joined McLaren in getting neither of its cars to the finish.
Nyck de Vries pitted on the same lap as Dennis, Cassidy, Hughes and Nissan stand-in Caio Collet, while Mortara's race came undone as he attempted to overtake da Costa for third through the fast Turn 10/11 Esses.
As he turned into the left-hand part of that sequence his left-rear wheel clipped da Costa's front wing - leaving the Porsche with damage but also spitting the Mahindra off onto the grass at high-speed with a puncture.