Earnhardt was a car-length ahead of Denny Hamlin when NASCAR threw the seventh caution of the race a split second before Earnhardt crossed the finish line to win the Great American Race for the second time in his career.
Under NASCAR's new Chase for the Sprint Cup format, Earnhardt's 20th career Sprint Cup Series victory almost assuredly locks him into the 10-race postseason playoff, set to start at Chicagoland Speedway in September.
Hamlin came home second as the race ended under caution, with Brad Keselowski, Jeff Gordon and reigning series champion Jimmie Johnson running third through fifth, respectively.
In Victory Lane, Earnhardt didn't even try to contain his elation. After all, he had just broken a 55-race winless streak. After finishing second in three last four Daytona 500s, he had just won the NASCAR Sprint Cup Series season opener in his last year with crew chief Steve Letarte, who is headed for the TV booth in 2015.
And he had just won his second Daytona 500 a decade after winning his first, holding off Hamlin in a dramatic two-lap dash to the finish.
"Man, winning this race is the greatest feeling that you can feel in the sport, aside from obviously accepting the trophy for the championship," Earnhardt all but shouted over the din of the celebration. "I didn't know if I'd ever get a chance to feel that again, and it feels just as good, if not better than the first because of how hard we tried year after year after year, running second all those years and wondering why and what we needed to do.
"I've got to get my head together ... This race car was awesome. We showed them all night long how good a car we had, and it's because of these guys right here (his team) putting it together in the shop. We could fight off battles after battles. We got a little help from Jeff (Gordon) to get away on that (last) restart and tried to take care of it from there.
"This is amazing. I can't believe this is happening. I'll never take this for granted, because this just doesn't happen twice, let alone once. I'm so thankful. Thanks to all my fans out there for supporting. We pretty much might be in the Chase? We get that off our chest and we are two-time Daytona 500 champion!"
After a rain delay of 6 hours 22 minutes, the race ran-caution-free from a restart on Lap 47 to Lap 145, when a wild 13-car wreck in Turn 4 thinned the field.
On the inside of a three-wide trio with Brian Scott and Aric Almirola, Kevin Harvick drifted up the track and clipped Brian Scott's Chevrolet, sending Scott into Almirola's Ford and turning it sideways.
Almirola hit Danica Patrick's No. 10 Chevrolet, which shot nose-first into the outside wall in the tri-oval, destroying the car. The No. 3 Chevy of polesitter Austin Dillon also sustained damage but remained on the lead lap.
Dillon's Richard Childress Racing teammate, Paul Menard, wasn't as fortunate. His No. 27 Chevy, which had led 29 laps, was heavily damaged and lost 14 laps as his team worked feverishly to repair it.
"What the hell happened?" Patrick said, as she slid to a stop in the soggy infield grass.
Sixteen laps after the first major incident of the race, Dillon's Chevrolet got loose and tapped the No. 42 of fellow rookie Kyle Larson, triggering an 11-car wreck that slowed the race. At Lap 184, 2011 Daytona 500 winner Trevor Bayne slammed into the outside wall on the backstretch to cause the fifth caution of the race.
On Lap 194, contact between Dillon and the No. 31 Chevrolet of RCR teammate Ryan Newman ignited a seven-car wreck in Turn 3 that set up the wild finish. Earnhardt, who was in the lead, ran over the swatch of Bear Bond (tape) from Newman's car under the yellow and tried in vain to remove the tape by driving within inches of the pace car.
First out of the race was Martin Truex Jr., whose luck turned from bad to worse on Sunday. With his primary car destroyed in a last-lap wreck in Thursday night's Budwesier Duel at Daytona, Truex had to give up his second-place starting position and take the green flag from the rear of the field in a backup car.
On Lap 32, Truex's engine expired after the oil pump belt dislodged, forcing an early exit from a race the driver of the No. 78 Chevrolet thought he had a chance to win.
"The car was super-fast today, and I went to bed last night thinking that this was my best shot ever to win the Daytona 500 and really felt that way, even today," Truex said. "The car was just so good, and we were just riding around and biding our time, being patient and trying to get to the end of this thing.
"Unfortunately, it wasn't meant to be."
It wasn't meant to be for Tony Stewart or Clint Bowyer either.
Stewart, in his first points race after missing the final 15 events of 2013 with a broken right leg, took his No. 14 Chevrolet to the garage with a fuel pressure problem after completing 118 laps, frustrated in his 16th fruitless attempt to win the Daytona 500. Bowyer's engine expired after 127 laps, relegating the driver of the No. 15 Toyota to a 42nd-place finish.
Stewart ended the race in 35th, 26 laps down.