Darlington, SC (Sports Network) - Regan Smith staged a major NASCAR upset by holding off Carl Edwards in a two-lap overtime finish to win Saturday's Showtime Southern 500 at Darlington Raceway.

Smith took over the lead when he opted not to pit, while most of the other leaders came in for a final round of stops during a caution in the closing laps.

After the restart, Smith continued to run in front when Kyle Busch, Kevin Harvick and Clint Bowyer wound up bumping into each during a three-wide battle coming out of turn four. Bowyer slammed hard into the inside wall. Busch then made contact with Harvick and sent him into the outside wall.

The incident setup a green-white checkered finish. Smith quickly pulled away from Edwards after the final restart, but Smith scraped the wall along the backstretch on the last lap, allowing Edwards to gain on him.

Smith managed to fend off Edwards at the finish by 0.2 seconds for his first win in his 105th career Sprint Cup Series start.

"The car was good all night, but we just didn't have track position," Smith said. "The opportunity showed up to stay out there. [Crew chief] Pete [Rondeau] made a great pit call. I was going to be mad if he didn't do that, but I was going to do what he told me to do. It worked out."

Smith became the sixth different driver to claim his first Sprint Cup win at Darlington.

"Legends are supposed to win this race; I'm not supposed to win it," he said.

Lake Speed was last driver to pick up his first Cup victory at Darlington in 1988.

This is Smith's third season with Furniture Row Racing, a single-car team that operates in Denver, CO.

"These guys have stuck behind me for three years now," Smith said of his team. "We've had some major ups and downs, and I think this win would be classified as a major up for sure."

On the eve of Mother's Day, Smith's mother was not able to be attend the 500- mile race due to her participation in tornado relief efforts in Tuscaloosa, AL.

While Smith took his victory lap around the tricky 1.366-mile Darlington track, tempers flared on pit road where Harvick pulled in front of Busch's car. Busch attempted to drive away from Harvick but was unsuccessful in his effort.

After Harvick hopped out of his Chevrolet and then approached Busch, who was still inside of his Toyota, it appeared that Harvick threw a punch at him.

"It's just uncalled for, and it's just unacceptable racing," Busch said. "It's in the last couple of laps, but I gave him room coming off of [turn] two, and I didn't get the room. It's just real unfortunate. I hate that we tore up a few good cars there."

Busch finished 11th, while Harvick settled for 17th. Both drivers were summoned to the NASCAR hauler for a discussion with race officials.

"We were doing what we had to do at the end, and things happened," Harvick said after his chat with officials.

Edwards' second-place finish came four days after his wife, Kate, gave birth to their second child -- Michael Edwards.

"[Smith] spun his tires a little bit on the restart," Edwards said. "I pedaled to make sure I didn't beat him across the line. Then Brad [Keselowski] pushed him, and I was scrambling. I thought, 'I hadn't planned on this.' I had planned on getting the lead."

Edwards widened his points lead to 23 over Jimmie Johnson, who rebounded from several issues during the race to finish 15th.

Johnson, the five-time defending series champion, spun around after Juan Pablo Montoya hit him from behind early in the race. He also spun around on lap 221. Johnson was later penalized for a missing lug nut during a pit stop.

Keselowski finished third, while Kasey Kahne, the pole sitter, and Ryan Newman rounded out the top-five. Kahne led the most laps with 124.

Denny Hamlin, Tony Stewart, Greg Biffle, Jamie McMurray and Martin Truex Jr. were sixth through 10th, respectively.

The race featured 11 cautions, including one on lap 230 when Brian Vickers and David Ragan made contact. Ragan's Ford tore off most of the left-side panel on Vickers' Toyota.