It was the championship leader’s second successive victory and his fourth of the season following triumphs at Long Beach, Barber and Indianapolis.
The Belardi Auto Racing man beat title rival Zach Veach, who had started from pole in his Andretti Autosport-run machine. Chaves passed Veach on lap seven and pulled away during the second half of the contest to win by close to eight seconds.
Britain’s Jack Harvey finished third to record his fifth podium finish of 2014 for the Schmidt Peterson Motorsports squad. Harvey closed in on Veach late on but couldn’t overhaul the American.
Matthew Brabham (Andretti Autosport) was fourth on the road but was later penalised for blocking, promoting Juan Pablo Garcia (Schmidt Peterson) to P4. Meanwhile the lone caution period of the race came after Luiz Razia hit the wall hard at turn two.
Chaves now leads Veach by a slender 11 points. The series’ grid hit a new low for the race, with only eight cars contesting the 40-lap event.