JOLIET, Ill. (AP) — Brad Keselowski began the season with a bit of goofiness, posting on Twitter during a red-flag stoppage at the Daytona 500.

He’s ending the year with a far more serious pursuit — for his first Sprint Cup championship.

Keselowski is off to a fine start after an impressive victory over Jimmie Johnson on Sunday at Chicagoland Speedway. In the opening race of the Chase for the Sprint Cup, the 28-year-old Keselowski outlasted Johnson for the first Chase win of his career. Keselowski also took over the lead in the points standings for the first time.

“There’s no better place to start than in the lead, right?” Keselowski said. “It feels like Round One of a heavyweight title bout. It’s a 10-round bout, and Week One’s done. We might have won the round, but didn’t by any means knock ‘em out.”

Keselowski and his No. 2 Dodge got ahead of Johnson after a crucial pit cycle with about 35 laps remaining and led the final 26 laps in the 400-mile race. Johnson finished 3.171 seconds behind, and he said he thought Keselowski crossed a restraining line too early when exiting after that pit stop near the end.

The incident was reviewed and there was no infraction called, and Johnson never made much of a run at catching Keselowski during the final laps.

“He did cut up early. It did impede my progress,” Johnson said. “But it didn’t affect the outcome, I don’t believe. The way he made quick work in traffic and stretched it out on me, I’m not sure I would have held him off. At the time it messed me up, but I don’t think it played an outcome in the race.”

All 12 of the Chase drivers finished in the top 18, with the exception of Jeff Gordon, who went into the wall with about 80 laps remaining. Gordon barely qualified for the Chase to begin with, and his championship hopes are already in serious jeopardy after his 35th-place showing Sunday.

It was Keselowski’s fourth victory of the season. The Michigan driver leads Johnson by three points — and gave Penske Racing a reason to feel good after Will Power’s failed bid for the IndyCar championship Saturday night in California.

“It’s a great day for us,” owner Roger Penske said. “It cools me down a little bit after being hot last night.”

Kyle Busch finished fourth, the best performance of any driver not in the Chase. Among other Chase qualifiers, defending champion Tony Stewart was sixth, Dale Earnhardt Jr. was eighth, Martin Truex Jr. was ninth and Clint Bowyer was 10th. Kevin Harvick finished 12th, one spot ahead of Greg Biffle.

Denny Hamlin, the top seed coming in, fell all the way to 16th in the race while low on fuel at the end, and Matt Kenseth finished 18th.

Stewart is third in the standings, followed by a three-way tie among Hamlin, Kahne and Bowyer. Earnhardt is seventh, followed by Biffle, Truex, Harvick, Kenseth and Gordon — who is 47 points behind the leader.

There were only four cautions for 23 laps, the last coming when Gordon needed to return to the garage with damage to the right side of his car. He said his throttle became stuck, causing the crash.

“Disappointing,” said Gordon, who started the race in 19th position. “We had to fight hard to come from 19th up there in the top five, and the car was feeling good.”

Keselowski has finished in the top 10 in 10 of the last 11 races. He began the year poorly with a late accident at Daytona. Earlier in that race, he caused a bit of a stir when he posted on Twitter during the red flag. Afterward, NASCAR said it was OK for Keselowski to keep his cellphone in his car during events, and that all drivers were encouraged to use social media.

Lately, Keselowski’s driving has been drawing the attention. He’s showing the consistency and maturity needed to make a run at the title.

“I just think Brad does a nice job. I think he prepares for the races, he knows what he has. He works really well with his team,” Kahne said. “As far as the championship, I don’t think anyone knows that until you actually win it.”

Johnson had won five titles in a row until last year, and it looks as if his No. 48 Chevrolet is a threat again. He won the pole this weekend and finished in the top 10 for the ninth time in 11 Cup races at Chicagoland — although he’s never won. He led 172 of the 267 laps Sunday.

“We all know how good his team is,” Keselowski said. “We all know how good he is, and look at the resume over the last six years. Hey, look at the resume over the last 10 years. It’s impeccable.

“To be racing him, whether it was for the lead or for 10th, is an accomplishment.”