A week is a long time in Chase politics: this time last week it seemed that Tony Stewart was running away with the 2011 NASCAR Sprint Cup championship; Kurt Busch was only just in the running, and five-time champion Jimmie Johnson's hopes of a sixth title were being written off.

Not so this week, after Busch and Johnson raced hard to the chequered flag ahead of Carl Edwards, but Tony Stewart's two-win Chase bubble finally burst with a 25th place finish.

The AAA 400 was run under permanent threat of rain, with slow-moving showers in the area showing up on the radar causing two of the race's ten cautions during the afternoon. But the rain never settled in for a stay and the action was quickly resumed, with the full 400 one-mile-lap distance completed over the next three and a half hours.

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Martin Truex Jr. led the field to the green flag, but Kurt Busch - starting alongside him on the front row - took over on lap 3 just before AJ Allmendinger got spun into a sideways slide by Denny Hamlin, miraculously managing to save the #43 from a huge wreck but bringing out the first caution of the day. Even as the track went back to green there were "sprinkles" reported over Dover International Speedway, and sure enough on lap 19 the yellows came out for rain.

It was a short delay and racing resumed four laps later with Busch out in front of Carl Edwards, Martin Truex Jr. and Kyle Busch. Dale Earnhardt Jr. was a lap down, however, having had his right-front sway bar break making the car unmanageable, but at least the caution laps had allowed him to have the problem fixed and it wasn't long before he won one of the free passes to get back onto the lead lap again, so it was a narrow escape and a nice piece of damage control from the Hendrick team.

A scheduled competition caution on lap 40 finally allowed everyone to come in for a proper stop and for fuel, and then there followed over 90 laps of green flag running without interruptions. Busch started this phase in the lead, but on lap 52 Carl Edwards finally pressed his claim and went out in front of the Busch Brothers, with Brad Keselowski having made up ground in the pit stops to run near the front with Jimmie Johnson. Greg Biffle joined in the fun, at least until he got a drive-thru penalty during the first round of green flag pit stops.

Just as he had done in the preceding day's Nationwide Series race, Edwards was putting on a masterclass and pulling out an ever more formidable lead. After the pit stops cycled through, he had a 5s lead over Kurt on lap 123 and looked unbeatable with only the traffic causing him any headaches: by lap 135 he had left just 18 cars on the lead lap.

Despite some mist and light rain during this period the track remained green until finally on lap 137 the yellows were out again, after Mike Bliss touched the wall while trying to avoid a slow Casey Mears. The leaders opted for a quick return to pit lane, while others a lap down used the opportunity to get the wave-around back onto the lead lap. When the track went green again, Edwards quickly took back the lead from Jeff Burton and once again started to disappear off into the distance ahead of Kyle Busch and Jimmie Johnson.

Kurt Busch had dropped back to sixth place after taking a chassis adjustment to cope with the track "rubbering up", and despite saying that the car was handling better he only narrowly saved the #22 from disaster on lap 173 when he got sideways off of turn 3, just before a caution came out for debris.

AJ Allmendinger won the race off pit road after a mix of strategies, followed by Kevin Harvick, David Reutimann, Jimmie Johnson and Carl Edwards, but the restart on lap 180 was short-lived when Bobby Labonte immediately went for a slide. When they tried again, Harvick took over the lead ahead of Johnson, while Edwards found himself stuck in traffic back in ninth and complaining of being loose. But Harvick's two-tyre strategy left him vulnerable, and so Johnson took over and pulled out a big lead as the race passed the midway point, becoming 'legal' even if the rain did move in from this here on. Matt Kenseth was also having a good stint and duly moved up to second, he and Johnson separating themselves from Kurt Busch was who leading the chasing pack.

The next round of pit stops - under green once more - started from lap 243, and they were a welcome sight for several cars including Harvick, who had dropped out of the top ten on waning form, and Keselowski whose performance had dropped off a cliff after power steering problems that put him a lap down. It also seemed like good timing for Edwards, who despite running in fourth still wanted the #99 tightened up a little. But it would prove to be a costly pit stop indeed for Edwards, after he was handed a drive-thru for speeding in pit lane, putting him a lap down in 25th place.

Another caution for rain on lap 256 enabled a return visit to pit lane for some, and when racing resumed on lap 264 Jimmie Johnson led Kenseth and Kurt Busch to the green flag. Ten laps later Johnson had a 2.3s lead over Kenseth, despite the #48 crew chief Chad Knaus repeatedly asking Johnson to be mindful of fuel conservation.

Edwards quickly recovered to 22nd position - first car off the lead lap after his pit lane speeding penalty - and stayed there until a debris caution on lap 300 following JJ Yeley hitting the wall in turn 4, which gave him the free pass back onto the lead lap at long last.

"We were very, very fortunate," Edwards conceded later. "As frustrated as I am with myself for messing that up, I'm really, really grateful for the gift that was given to us with that caution and the ability to come back up there."

The ensuing pit stops did little to shake up the order, and on lap 306 Johnson was still in front for the restart ahead of Matt Kenseth, Kurt Busch and Kasey Kahne. Johnson once again shot off into the distance, while Kenseth's challenge was fading and Kurt Busch took him for second place. There was little point in anyone trying to save fuel at this point - everyone would have to come in one more time, it was just a matter of picking the right moment or waiting for the right caution.

The ninth yellow duly arrived on lap 352 when Mike Bliss got loose in turn 2 and hit the wall. Everyone came in, with the top eight all opting for the two-tyre gambit, with Johnson still in front of Kurt Busch, Kasey Kahne, Kyle Busch, Carl Edwards and Kevin Harvick.

After having been perfect on the restarts all afternoon, suddenly Johnson's touch failed him and he handed the advantage to Kurt Busch, who jumped out in front, but the race was quickly back to yellow after Greg Biffle spun and hit the inside wall on lap 362.

There were 34 laps to go to the chequered when the race resumed, and everything depended on Johnson getting a good run on Kurt Busch to regain the lead and pull out a safe lead. But he didn't manage it: instead, the #48 spun its tyres and Busch was released to safety. Johnson managed to regain his momentum to hold off a hard-charging Carl Edwards who had arrived on his tail to challenge for the second spot, despite the #48 struggling in the closing laps when it strayed into the rubber build-up on track.

Everyone managed to hold station, and with the rain now a distant memory (there had even been some outbreaks of sunshine reported) and no more cautions, the chequered flag was soon out to welcome Busch, Johnson and Edwards home after 400 laps.

"It was just perfect execution today, with pit stops and with making the car better during the race," said Kurt Busch. "I couldn't be happier right now. To win a Sprint Cup race in the Chase, this is what it's all about."

His arch enemy of the past few weeks, Jimmie Johnson, was left ruing those last two restarts that had cost him the win. "I did a really good job, up until those last two," Johnson said. "I blew it by spinning the tires. Kurt got a good launch, and we were door to door going into 1, and he was able to get by on the outside," he explained. "And then the next one, I was going to try to do that same thing back to him, and I was just trying to time it when he was going to accelerate. And I didn't time it right.

"I put it on me, because the starts I had earlier in the day, regardless of the lane, leading or not. I cleared them typically going into 1 so, it's on me."

Kurt Busch had also been lucky that the early dominant runner, Carl Edwards, had shot himself in the foot with that mid-race pit lane speeding penalty. "I ruined it there on pit road," Edwards said. "That's about as small as you can feel in a race car. We talked about it before the race ... Bob [Osborne, crew chief] and I actually discussed the last section [and] how I was not going to speed through it. And I just blasted right through it."

Edwards thanked his pit crew for sticking by him after his error, "Because they had every right to be really, really upset with me. So it ended up being a good finish."

Edwards' third place was enough to boost him into a share of the points lead in the Chase with Kevin Harvick, who recovered from that mid-race dip to finish in tenth place. Kurt Busch's victory was enough to put him into a share of third place with Tony Stewart, whose two-race winning streak came to an end with a bump at Dover after never overcoming a poor qualifying effort and failing to put together a setting that really worked on the concrete Monster Mile.

"Obviously the main thing that put us behind was just our qualifying effort, and just starting so far back," said crew chief Darian Grubb. "The biggest thing, though, was just that we don't have the concrete tracks figured out ... We just need to figure out what we need to do. It's not because of a lack of effort."

Jimmie Johnson - all-but written off after last weeks' race - is straight back into contention in fifth place thanks to his second place at Dover. He's just ahead of Kenseth and Keselowski in the points, but only 20pts cover the top nine Chase contenders after three races.

Falling somewhat out of contention are Dale Earnhardt Jr. (who followed up his early sway bar problem with a wheel problem that forced him into an unscheduled pit stop that dropped him to 24th place by the end), Ryan Newman and Denny Hamlin.

Newman - like his team mate and car owner Stewart - confessed that they just had been in bad shape all weekend. "The whole package," he replied when asked what the problem been. "Even when we got the balance halfway decent, the car didn't have speed. So we just missed it."

It could all change again for Stewart-Haas next week at Kansas, but the fact remains that the Chase contenders are fast running out of races to make their mark on the 2011 championship battle.

Full race results and times available.