“I knew it would take a mistake-free race to win, and I was proved right,” Busch said. “It means everything to win this championship again. There were a lot of doubters when we won the first one.”

Busch’s first title, in 2015, came after he had earned an injury waiver to excuse him from missing much of the first half of the season because of a broken leg and foot he sustained in a crash at the season opener. Usually, drivers must contend every race of the series to be eligible for the title.

“I can’t wait to get ready to chase a third title next year,” he said on Sunday. “Titles are my legacy, and I want to win a bunch of them. I think I should have more titles than this already.”

In fact, Busch is now the only active series driver to have more than one championship to his credit, except for the seven-time titlist Jimmie Johnson. According to NASCAR, Busch has more wins this decade than any other driver in the series. The win also gave him 56 career Cup Series victories, giving him sole possession of ninth on the career list, one ahead of Rusty Wallace.

Busch started the race in fourth; qualifying had been rained out, so the starting order was determined by points, with Hamlin in the top position.

After some initial trading of positions, Truex pulled away from the pack. He led until the first round of pit stops — only 37 laps into the 267-lap contest. All of the contenders complained of a high rate of tire wear. The weather was also a factor; it was only 67 degrees for the first lap, an unusually low temperature. A cold front went through the area on Friday.

After Busch emerged as the winner and champion, the team owner Joe Gibbs dedicated the moment to his son, J.D. Gibbs, a co-founder and former president of the team who died in January.

“This is a very emotional victory for our team,” Joe Gibbs said. “We did it for J.D. This whole season is dedicated to him.”