Sunday's AAA Texas 500 proved to be a curious race of two very distinct parts: a lengthy, uneventful preamble that had even the most ardent fans shifting uneasily in their seats waiting for something to happen; and then a thrilling final 25 laps during which the simmering championship battle between Jimmie Johnson and Brad Keselowski broke out into open warfare.

Johnson had won his second consecutive pole on the 1.5-mile Texas Motor Speedway, and led the field to the green flag with every intention of also claiming his second consecutive race win as well, to match his success last weekend at Martinsville that had put him into a slender lead in the Chase standings. Johnson was easily able to convert pole to a lead that lasted for the first 100 of the 335 laps of the race, save for a couple of laps during the first cycle of green flag pit stops.

There were no cautions for that first hundred laps either, and only on lap 101 did the yellows finally come out - and then for debris. Even though everyone had just completed their second round of pit stops under green, almost everyone took the opportunity to make a slightly less pressured visit to pit road. Ryan Newman was the exception, and Brad Keselowski took only two tyres, so they lined up on the front row for the restart ahead of Johnson, Kyle Busch and Clint Bowyer.

However, the old axiom of cautions breeding cautions came into play: after that unbroken first century, the yellows flags proved a hard habit to break at the restart. First there was AJ Allmendinger, spinning the #51 Phoenix Racing car in turn 3. A run through the grass did enough damage to make it impossible for Allmendinger to continue, in what is his last scheduled Cup race of the season, with the car being handed over to Regan Smith for the last two outings of the season.

"If this happens to be my last race in Cup thank you to all the fans that supported [me] especially in the last 4 months. Cant say thank [you] enough," Allmendinger said in a notably elegiac post on Twitter after the premature end to his Sunday outing. "I let the whole team down today. Meant the world to me they gave me another chance. They are [a] great group of guys and the hardest workers I have ever been around."

The next restart attempt was quickly thwarted when Bobby Labonte got into the back of Trevor Bayne's car, causing a tailback that caught out the traffic behind and ended up with Juan Montoya running into the in-field grass area. All three cars involved received damage, with Labonte and Montoya both going over 50 laps down while getting repairs in the garage.

"It's kind of a tough break," said Montoya. "You see the leader going, you go - [but] they all checked up and [I] got on the brakes. These things don't slowdown that well so I went left to go through the grass to avoid the wreck.

"I don't know there is like a manhole cover there or something," he explained. "The car took off like two or three feet in the air; same thing as the #51. The crazy thing is we are not even up to speed yet. I mean I went from second, shifted into third, got on the brakes, went left and the car just flew up in the air. I hit something; you look at the #51 and the same thing. There is something there like a big step there in the middle of the grass and it kind of breaks race cars in half."

Finally on lap 129 the race was able to find a restart that took: Jimmie Johnson surprised no one by quickly pulling away from Brad Keselowski, Kyle Busch, Clint Bowyer and Martin Truex Jr. at the green flag, and the field settled in for another lengthy spell of racing that lasted almost 60 laps through another round of green flag pit stops until debris materialised in turn 1 on lap 186.

Little had changed in the running order, and when the race restarted Jimmie Johnson was still ahead and was dutifully followed by Kyle Busch, Brad Keselowski, Martin Truex Jr. and now Jeff Gordon in fifth. But with the sun now low in the sky and shadows starting to fall on the track, conditions were changing and for the first time Johnson didn't have the best car on the speedway - he was passed by Kyle Busch and Brad Keselowski, although he looked comfortable enough running in third place albeit two seconds off the new leading pair.

Another debris caution on lap 224 did little to change the order at the front, but at the restart Busch was complaining of a vibration and he started to fall back, with Keselowski taking over the lead. Jeff Gordon surged into second place ahead of his team mate Jimmie Johnson, but then had a tyre go down which forced him to make an unscheduled extra pit stop just before a new debris caution on lap 275.

Busch picked up his lost places in the ensuing round of pit stops to take the restart ahead of Johnson and Clint Bowyer, while Keselowski had problems locking his brakes on his approach to his pit stall and dropped to ninth place; his overshoot also held up Danica Patrick, who had the next stall along on pit road and who couldn't get in to make her own stop until Keselowski was sorted out.

The timing of this latest stop had temporarily converted the marathon race into one of fuel conservation with everyone fretting about hitting their fuel numbers, saving an extra lap's worth of gas, and hoping to make it to the end without any green-white-chequered dramas. Johnson in particular was finding the fuel saving to be a pain, and he grew even more concerned when it appeared that Keselowski was managing to save gas while still running fast enough to recover most of those lost positions at the same time, popping back into fourth place with 25 laps remaining.

But that was the point when things started to get really interesting: Marcos Ambrose was the trigger, when he crashed into the wall on lap 311 to bring out the seventh caution of the day. Immediately, all thoughts of fuel saving went out the window as the leaders came onto pit road: Keselowski and his crew chief Paul Wolfe attempted to out-strategise their rivals by taking only two new tyres at this stop while the others went for four, which meant that the #2 emerged from pit lane ahead of Busch and Johnson.

Keselowski took the inside line at the restart and cleared for the lead, although Johnson was not happy with what he saw as the #2 car jumping the flag to do so. Johnson's crew chief Chad Knaus tried to calm his driver down, admitting that NASCAR didn't seem minded to do anything about the perceived infraction and that in any case the #48 was strong enough to take care of it in the remaining 15 laps of the race.

But before Johnson could press his claim on the lead of the race, they were back under caution. Johnson's Hendrick Motorsports stablemates Jeff Gordon and Kasey Kahne had made light contact that left Kahne with a tyre going down - which ended up with the #5 car grazing the wall and forced a reluctant NASCAR to throw a new yellow for debris left on the track by Kahne's car. Both Kahne and Gordon ended up having to go to pit lane for repairs, but none of the other race leaders were about to give up track position at this point in the proceedings.

The restart on lap 327 saw a true declaration of hostilities between Keselowski and Johnson who were starting alongside each other on the front row: Keselowski was running down low, and when he moved up the race track he made repeated sideways contact with Johnson who was finally forced to lift, ceding the lead to Keselowski.

Johnson wasn't happy about what had happened, and subsequently gestured angrily at Keselowski through the side window: "Just wanted him to use his head," explained Johnson. "There is no sense in taking us both out in the process. If he was taking me out, you can count on the fact that I would have been on the gas and trying to take him with me."

That should sealed the race in Keselowski's favour, but in a packed field behind the leaders Mark Martin received a tap from Carl Edwards and went for a spin in turn 4 on lap 331, putting him firmly into the wall and forcing the ninth caution of the race - and one that triggered green-white-chequered overtime conditions. Johnson and Keselowski would have one last shoot-out opportunity, and providing the field made it round to the white flag then whoever won this final duel would be heading to victory lane.

Having been caught out twice already, Jimmie Johnson was in no mood to make it three in a row. He allowed Keselowski no comeback as the race went green, taking the lead on the outside and keeping it all the way to the chequered flag two laps later.

"It was an awesome race," said Johnson as he celebrated the win. "The gloves are off and it's bare knuckle fighting ... That second to last restart was pretty sketchy a couple of times how close we were and how hard we were racing. Luckily we brought the cars back, another caution came out and got a great restart and got by him."

As for the flaring of tempers after that bruising penultimate restart battle, Keselowski moved to defuse any chance of a feud breaking out by making sure he offered Johnson a handshake in victory lane, which Johnson described as "very classy" of his rival.

"The cool thing about it is we walked right up to that line, got right to the edge, and then it stopped," said the five-time champion. "I have a lot of respect for that #2 team. Those guys are doing a great job. Today I think our cars were pretty equal throughout the course of the race and at the end of the race we were on four [tyres] had to take advantage of it."

"I knew I wasn't going to be able to execute every restart, and Jimmie did a great job on the last one," admitted Keselowski, who came home in second place. "I had to choose between wrecking him and winning the race, and it didn't seem right to wreck him."

Finishing in third place, Kyle Busch had the best seat in the house to watch those final three restarts, and was impressed by what he'd seen.

"It was exciting," he said. "Those guys up there, man, they were battling, and they battled hard, giving it everything they've got. That's what they've got to do. [To] win a championship in the Sprint Cup Series, that's what you're going to have to make of it." You could tell he was making notes for 2013, when he clearly intends to move Heaven and earth to make the Chase.

The next four cars behind Busch were all 2012 Chase contenders - Matt Kenseth clinched fourth ahead of Tony Stewart, Clint Bowyer and Dale Earnhardt Jr., while Kurt Busch finished in eighth place for his new Furniture Row Racing team ahead of Kevin Harvick and Greg Biffle to round out the top ten.

By holding on to second place at Texas, Keselowski ensures that Johnson has extended his Chase lead by just 5pts this week, and the championship remains very much open heading into Phoenix and Homestead-Miami.

"It's a small amount of control, but we're definitely in control," said Johnson of the title battle ahead. "There is not going to be any breathing easy until the end. Breathing a little bit better. I was two points and now we've got seven, but there is a lot of racing left. We are running up front, running one-two all the time [but] it doesn't mean it will be that way for the final two races."

"It don't feel good, but there is a part of you that just feels like you're first in class," said Keselowski of slipping further behind Johnson in the standings. "I'm confident that it will come back around, and when it does, we'll change these seconds and fifths or whatever they are over the last few weeks into wins."

With just those two races remaining in the 2012 season, ten drivers remain mathematically in contention for the Sprint Cup championship. But Texas did see the end of the title road for two of the Chase field, with Kevin Harvick and Dale Earnhardt Jr. now both ruled out of the running despite their top ten finishes at Texas.

Harvick's race at Texas had been slightly hampered by an unprecedented pre-race event, when a sandbag used by one of the parachute jumpers taking part in the build-up entertainment fell on the #29 where it was lined up on pit road.

"Never good when the day starts with a parachute weight hitting our car," Harvick tweeted after the incident. "Welcome to 2012," he added, saying that it summed up his frustrating year.

While the damage to Harvick's car was mainly cosmetic, it still required the team to take the car back into the garage for 30 minutes of hurried repairs before the command to start engines was given by actors from the TV series Dallas. The parachutist himself was not injured in the incident, although he made an awkward landing after coming in low over pit road.

Full race results and Saturday practice times as well as Sprint Cup Championship standings are available.