Dale Earnhardt Jr. took the points lead from Jeff Gordon, who fell to second, five points back. Allmendinger's win reduced to four the number of Chase transfer spots now available to winless drivers. Winless Greg Biffle, who entered the race clinging to the last spot, dropped out of the boundary by eight points despite finishing eighth. Winless Kasey Kahne finished 12th to drop 12 points from the transfer spot.
After a restart with four laps left, Ambrose passed Allmendinger for the lead, but surrendered it entering Turn 1 as a caution flew for simultaneous but unrelated crashes involving Alex Kennedy and Denny Hamlin.
Allmendinger maintained the lead on a restart, and after a tenacious door-to-door tussle with Ambrose around the 2.45-mile course, pulled away to win by 1.16 seconds.
Pole sitter Gordon dueled with Ambrose for the first half of the race, but his No. 24 Chevrolet was stricken with an electrical problem on Lap 50 that dropped him to 40th after a lengthy pit stop. He finished 34th.
The race was red-flagged three times, once for 81 minutes after a vicious wreck in Turn 5 on Lap 57. Michael McDowell's No. 95 Ford was sent airborne, its dislodged rear housing shredding a section of metal barrier, after striking Ryan Newman's No. 31 Chevrolet. Newman had nosed hard into a similar barrier on the right side of the track and careened back into McDowell's path after apparently being nudged by Greg Biffle. Newman and McDowell were evaluated and released from the infield care center.
After others suggested he played a key role in the crash, Newman rebuked the lack of modern safety barriers at a facility where wicked airborne crashes have become typical.
"The SAFER barrier doesn't exist here. There are no concrete walls," he said. "It's just a very antiquated racetrack and the safety is not at all up to NASCAR's standards, and it's a shame that we have to have accidents like that to prove it."
NASCAR vice president of competition Robin Pemberton defended the use of so-called Armco barriers in a carousel area where high speeds and a narrow racing surface have proved a combustible combination.
"Not all places are places for SAFER barriers," he said. "There are different types of systems to slow the cars down."
The aftermath of Tony Stewart's fatal collision with Kevin Ward Jr. dominated the tone of the morning inside the garage and in the Twitterverse and cable television and radio, with debate churning over Stewart's motives and his, NASCAR's and his sponsors' responsibilities.
Although Stewart-Haas Racing competition director Greg Zipadelli said in the morning that the team was "business as usual" following the incident at Canandaigua Motorsports Park in upstate New York, the team announced at 10:15 a.m. ET that Stewart had opted not to compete. Stewart released a statement within a half hour after the race, saying, "There aren't words to describe the sadness I feel about the accident that took the life of Kevin Ward Jr. It's a very emotional time for all involved, and it is the reason I've decided not to participate in today's race at Watkins Glen. My thoughts and prayers are with his family, friends and everyone affected by this tragedy."
Ward's family issued a statement of appreciation for the racing community's support and asked for time to grieve.