Johnson had shared the mark of seven victories on the concrete mile with Bobby Allison and Richard Petty. Led by Johnson, the entire top 10 on Sunday was made up of Chase for the Sprint Cup championship drivers.
"To do anything that Richard or Bobby has done is quite an accomplishment," Johnson said.
Earnhardt had one of the fastest cars, but he missed pit road and gave up the lead early in the race. He had a strong enough No. 88 Chevrolet to get back into the race and contend for his first victory this season but couldn't pass Johnson.
"We left everybody in the mirror. We were clicking off some laps," Earnhardt said. "But just not fast enough to get to Jimmie."
Kenseth kept his points lead even as he fell short in trying to become the first driver to win the first three Chase races. He holds an eight-point lead over Johnson as the Chase shifts to Kansas.
"I know that 20 is going to be awfully strong for the rest of the stretch," he said.
Johnson dominated as he usually does at Dover and led 243 of the 400 laps to help extend his Chase record with his 23rd victory in 93 starts in NASCAR's version of the playoffs. He swept Dover in 2002 and 2009 and won races in 2005, 2010 and 2012.
Johnson has his sights set on a bigger piece of NASCAR history. He's in the hunt for his sixth Cup championship, which would put him one behind Petty and Dale Earnhardt Sr. for most in series history.
He caught a huge break when Earnhardt slowed during a green-flag pit stop and missed the entrance to pit road. He went from holding a 3.7-second lead on Johnson to trailing by more than nine seconds after he finally made his stop.
Johnson took the lead — and took off. Even smart pit strategy that included a late four-tire stop wasn't enough to boost Earnhardt past his Hendrick Motorsports teammate.
"The mistake I made coming on to pit road and missing pit road completely [cost us]," Earnhardt said. "If I had not given up that track position and had a smart enough race to keep the lead when it counted, right at the end we might have won the race. It would have been hard to get by us just like it was hard to get by Jimmie."