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Matt Kenseth started his Chase for the Sprint Cup championship in high gear by winning Sunday's Geico 400 at Chicagoland Speedway, a race delayed more than six hours due to rain.

Kenseth, who entered the Chase as the top seed, passed Kyle Busch after a restart with 23 laps to go and then held off his Joe Gibbs Racing teammate at the finish by 0.75 seconds for his series-leading and career-high sixth win of the season. Kenseth received pushing help from Kevin Harvick before he overtook Busch following the last restart.

The 400-mile race at Chicagoland was scheduled to begin shortly after 2 p.m. ET, but concluded under the lights just past midnight. After the start was delayed by about 90 minutes, the event ran for 109 laps before heavy rain moved over this 1.5-mile racetrack, causing another delay for more than five hours.

Kenseth was leading the way when NASCAR halted the race for poor weather conditions.

"I was worried about the rain, and the track conditions in the nighttime," Kenseth said. "I thought we were going to be better in a hotter, slick condition. But just shows I don't know what I'm talking about. We had a good car, had great pit stops, great strategy and had that restart at the end. That push from Kevin got us out in front where we really needed to be."

The weather wasn't the only thing that put a damper on the first Chase race. It came after a week-long of turmoil in NASCAR's top series following the controversial finish in last weekend's regular-season-ending race at Richmond. NASCAR spent the week investigating several teams in their attempts to manipulate the outcome of the event there. Ryan Newman was placed in the Chase and Martin Truex Jr. bounced out due to severe penalties assessed to Michael Waltrip Racing. On Friday, Jeff Gordon was added as the 13th driver in the playoff field, resulting from what NASCAR Chairman and CEO Brian France described as "an unprecedented and extraordinary set of circumstances that unfolded in multiple different ways" at Richmond.

NASCAR met with all Sprint Cup Series teams on Saturday to discuss its officiating changes and address the subject of teams artificially altering the outcome of a race.

During Sunday's pre-race drivers' meeting, NASCAR announced rules changes affecting the double-file restart procedure. When the green flag waves for a restart, the second-place runner is now allowed to pass the leader before they reach the start-finish line.

"There at the end, I thought I got a good enough restart, wasn't great, but I had enough going with the 20 (Kenseth) beside me," Busch said. "Then the 29 (Harvick) pushed the 20 by me before I got to turn one. I didn't have enough to stay on his door to hold him back to be alongside of him through (turns) one and two on the backstretch to try to race him in three and four. Once the 20 got out front, I was a little too loose. Just couldn't do anything with him. That was the race right there."

Busch's second-place run came after he won Friday's Camping World Truck Series race and then Saturday's Nationwide Series event here.

Harvick finished third, followed by Kurt Busch and Jimmie Johnson, who bounced back from two pit-road blunders. Johnson had finished no better than 28th in the previous four races.

"In the next-to-last run, we got ourselves right back in the thick of things, but unfortunately, we just didn't have the speed there at the end to be able to race for the win," Johnson said. "From the jack failing to the call on pit road for the lug nut not supposedly on, a variety of issues, it was a great comeback."

Gordon, who is Johnson's teammate at Hendrick Motorsports, rebounded from a flat tire, which put him one lap behind just past the halfway point.

"That was an incredible accomplishment," Gordon said. "To be able to come up through there and get sixth was a lot of fun. This is what we needed to get this thing started off right."

The top-six finishers are all in the Chase field. Brad Keselowski, who failed to qualify for this year's playoffs, took the seventh spot. Keselowski won at Chicagoland one year ago and then went on to capture the Sprint Cup championship. Ricky Stenhouse Jr., a rookie, scored his career-best finish with an eighth-place run. Chase drivers Clint Bowyer and Newman completed the top-10.

With the win, Kenseth holds an eight-point lead over Kyle Busch and an 11- point advantage over Johnson.

Kenseth collected the maximum 48 points after he led the most laps with 89.

"Every single point, every position is equally as important from here all the way until the last lap at Homestead," he said. "So you want to get as many points as you can get each and every week. We did a great job of that this weekend."

Dale Earnhardt Jr. and Joey Logano took a big hit in the championship Chase standings after both drivers suffered engine failure late in the race. Logano trails Kenseth by 52 points after finishing 37th, and Earnhardt's 35th-place finish put him 53 points behind.

Logano has placed outside the top-20 in the last two races after he had scored six straight top-10 finishes, including a victory last month at Michigan, which helped him get into the Chase.

"It's a bummer for this team," Logano said. "We did everything that we needed to do this week to give us a shot at this championship. We sat on the pole, led laps."

The remaining title contenders and their finishing positions include: Carl Edwards (11th), Kasey Kahne (12th) and Greg Biffle (16th).

Race 2 in the Chase is next Sunday at New Hampshire.