The Chip Ganassi Racing driver moved to the top of the standings by finishing third behind first-time winner Kyle Kirkwood and his Andretti Autosport team-mate Romain Grosjean.
Ericsson, who started on the front row on a street course for the first time, lost out to Team Penske’s Josef Newgarden in the pits when the majority of the field stopped under yellow, and then on the lap 25 restart was passed by O’Ward between Turns 7 and 8.
However, the 2022 Indianapolis 500 winner was then held up when McLaren driver O’Ward also tried to nose inside leader Kirkwood and spun, partly blocking the track.
Ericsson got going again but had slipped to eighth before he mounted his recovery to third.
Combined with his victory in St. Petersburg and eighth at Texas Motor Speedway, the result was enough to send him to the top of the championship table.
“It was a great weekend for us,” the Swede said afterwards.
“The only sort of issue we had in the race was that restart when Pato decided to dive down there and try to take out a lot of cars. Got caught out in that. Had to almost stop the car. I think I lost five or six positions there. From there on, it was tough.
“We had the pace in the car to fight for the win. So it was a good recovery to come back and still finish on the podium. The pace on the last stint was amazing.”
Asked to assess his chances had he not been delayed by O’Ward causing a track obstruction, Ericsson replied: “We had a good chance at it. We were running second behind Kyle [in the first stint]. I think we had a bit more pace than him, especially at the end of the race.
“It's tough on a street course to overtake. Kyle did a great job, deserved the win.
“But we definitely could have given him a run for it in the end there. We had to bounce back.
“I was happy to be able to make some good overtakes on my way back to the podium. I'll take that, we're back in the championship lead.
“Of course, could have, would have, should have. Maybe we could have challenged for it but it wasn't our day, and we're happy with that.”
Ericsson remarked that being back at the top of the points, as he was after six rounds last year, will give him confidence for the upcoming races.
“Last year already, we were fighting for the championship and leading the championship for a long time,” he recalled.
“I was disappointed to miss out on that but used that as motivation this winter to work hard on myself and my team. We've come out even stronger this year. Winning in St. Pete showed that.
“We're definitely in the fight.”
