"I just made a mistake at the end there and lost the race," Ambrose said Sunday after dominating the Nationwide race, only to finish second. "I feel pretty devastated."
The despair was real on a day that started in sunshine and turned to gloom. Ambrose led 60 laps over the 14-turn, 2.7-mile street circuit -- including 31 in a row when rain moved in for the second year in a row.
But after overcoming restart after restart in the crash-filled event, Ambrose slipped up at the wrong time. Edwards passed him on the final turn for his first career road win and the first Nationwide road triumph for Roush Fenway Racing.
"I can't believe I won the race," Edwards said. "I just figured he'd take off and run away with it. I guess that goes to show you you never give up."
Edwards won a two-lap sprint to the finish on a track that was both wet and dry in spots from a light rain. On the 76th and final lap, he closed fast on Ambrose entering Turn 10, a right-handed hairpin, and that gave Edwards renewed hope.
"I drove a little bit deeper than him and I caught him, and that surprised me," Edwards said. "I didn't think I'd catch him in that corner, but I had the benefit of watching his car. He was kind of out there flying. Once I got to him, we came off Turn 10, he was spinning the tires, and I thought I might have him."
Seconds later, Ambrose slid sideways after hitting the rumble strips in Turn 14. Edwards slipped past and outraced him down the final straightaway.
"That was an amazing gift," Edwards said. "Marcos just made that one mistake that gave me a chance to get by. The difference was the tires and the way the track was changing. As soon as it gets dry, there's so much more grip, and there were places out there I saw that had a little more grip. Maybe I could just see better through my windshield."
Ambrose survived three other restarts in the final 12 laps of the race, which was plagued by 11 cautions. The race went two extra laps and lasted 3 hours, 49 minutes, 19 seconds, the longest in Nationwide Series history. The Gateway 300 in 1997 lasted 3:48.25.
Ambrose was out to right what went wrong in the previous two Nationwide races at Circuit Gilles Villeneuve. In 2007 he led 37 laps and was challenging for the win before he was spun out by Robby Gordon and finished seventh.
Last year in the rain, Ambrose led 27 laps but was caught speeding on pit road late in the race and Ron Fellows won the rain-shortened event, the first points race in NASCAR history to be run on rain tires.
Ambrose and Edwards were supposed to drive together in the Grand-Am Rolex Sports Car Series race here on Saturday, but Edwards wrecked the car on the warmup lap and both had to watch the race.
"First he wrecks my sports car and then he steals a win from me," Ambrose said. "I'm starting to think I don't like him."
It was the third win of the year and 23rd in his Nationwide career for Edwards, who moved within 192 points of series leader Kyle Busch.
Points leader Kyle Busch went from fourth to 10th on the final two laps.
Ambrose started from the pole and was out front most of the race. But everything changed when rain moved in, halting the race at the end of Lap 61 so the teams could switch to rain tires, slap on windshield wipers, and hook up brake lights in a five-minute window.
The red flag lasted 6 minutes, 51 seconds, and the race resumed on Lap 64 with the street course damp but with no standing water like a year ago.
Ambrose quickly cleared the second-place car of Ranger. Edwards then tangled with Ranger and Busch slipped past both for second, with Edwards and Ranger right behind.
Ambrose had a 2.8-second lead after the first time around, but the ninth caution of the race, for debris, erased that margin on the next lap.
Ambrose again assumed control when the race went green again on Lap 68, but several cars spun out before the 31 cars remaining in the race made a complete trip around. That brought out caution No. 10, six more than last year's race and twice as many as 2007.
Ambrose easily drew clear on the restart on Lap 71 and Ranger passed Busch for second. But Steven Wallace set up the two-lap dash to the finish when he made contact with Victor Gonzalez and slid sideways into a big pack in the second turn to bring out the race-changing final caution.