A fast racecar and a two-tire change on the final pit stop had Carl Edwards doing his signature back-flip for a second Sunday in a row, as Edwards led a Roush Racing sweep of the top three positions in NASCAR's Dickies 500 at Texas Motor Speedway.

With his second consecutive victory on stock-car racing's elite circuit, Edwards vaulted to third in the point standings and transformed himself, in just his first full season in the Nextel Cup ranks, into a contender for the 2005 championship.

But a sixth-place finish by points leader Tony Stewart was good enough to preserve his status as the favorite to win his second NASCAR title. With two races remaining before the champion is crowned, Stewart holds a 38-point lead over Jimmie Johnson, who finished one spot ahead of Stewart (fifth) on Sunday, and a 77-point lead over Edwards.

Stewart doesn't have to be dazzling over the next two weeks to win the championship. He just has to be good. Should he go on to win NASCAR's championship in Homestead, Fla., on Nov. 20, the achievement would give his car owner, Washington Redskins Coach Joe Gibbs, as many NASCAR titles (2000, 2002, 2005) as he has Super Bowl titles (1983, 1988, 1992).

"It's not even really worth worrying about the points," Stewart said. "It's about worrying what you do to win the race the next couple of weeks."

Trailing Edwards across the finish was his teammate, Mark Martin, who led with three laps to go and battled valiantly on worn-out tires to keep Edwards behind him, but in vain. Matt Kenseth finished third to complete the sweep for Roush Racing and Ford.

Fireworks exploded over the backstretch of the 1.5-mile superspeedway after the checkered flag fell. Martin pulled his Ford alongside Edwards's to offer the first congratulations. And Edwards, after coming to a stop at the start-finish line and performing his celebratory back-flip off the top of the driver's-side door, was quick to shower his crew chief and team members with credit for the victory.

Had it not been for the decision to change right-side tires on the final pit stop, Edwards said, he never could have zoomed past Martin to collect his fourth victory of the season. With races at Phoenix and Homestead, Fla., remaining to settle the title, Edwards said his team relished the challenge.

"We're not changing a thing," said Edwards, 26, of Columbia, Mo. "We're going out to win this championship, and we're gonna do it by having fun. We probably won't beat Tony Stewart; the guy knows how to win championships. But that's not going to stop us from giving 100 percent."

For Martin, it would seem that seeing a victory slip through his grasp with two laps to go would leave him bitter, if not bittersweet. Not so.

"I don't like getting passed at the end. Ever," said Martin, 46. "But I'm not disappointed because I wasn't robbed. I got beat. I can deal with that. The guy that you can't deal with is Tony Stewart. He runs in the top 10 every single race. You can't beat that. You're not going to beat it. Not until something gives."

It's hard to make up 38 points, much less 77, on a smart driver in two races. That's because not only does the challenger have to have exceptional luck and skill, the front-runner has to stumble, as well. And Stewart has shown an uncanny ability to avoid missteps since NASCAR's 10-race postseason began in September.

That's what he did at Texas on Sunday, even after his car's handling deserted him when the sun set and track temperatures cooled. And even after Martin scraped the side of Stewart's Chevrolet with about 30 laps to go as they battled door-to-door for the lead.

But it was a costly race for Greg Biffle, who entered the race third in the standings and dropped to fourth (trailing Stewart by 122 points) after fending off one calamity after another to finish 20th. Had it not been for Biffle's spectacular spin through the front-stretch, however, the first half of the race would have been uneventful.

Eager to close his deficit to Stewart, Biffle seized the lead on Lap 37 but had to pit under the green flag after sensing a tire vibration. The team changed four tires as a precaution, which put Biffle one lap down. As he battled to get back on the lead lap, Biffle lost control of his car as he rounded Turn 4 with Dale Earnhardt Jr. closing on his bumper. Biffle spun around twice, kicking up plumes of smoke, but didn't hit anything, collected himself and carried on, only to spin out again in the waning laps.

Ryan Newman also lost ground, dropping from fifth to seventh in the standings, after a miserable day in a back-up car that wasn't nearly as stout as the pole-winning Dodge he wrecked in Friday's qualifying session.

The best racing didn't come until fewer than 30 laps remained. Stewart had taken the lead by then, but Martin ran him down. The two swapped the lead three times over two laps, battling hard for position. Contact between them threw a wrench in Stewart's handling, and he drifted back, leaving the Roush teammates to dice among themselves for the victory.

NASCAR Note: Also Sunday, Joe Gibbs Racing announced that Denny Hamlin will drive the No. 11 FedEx car for the rest of the season and 2006. Hamlin, who finished seventh in the No. 11 on Sunday, has impressed in his tryout after taking over for Jason Leffler, who was fired in August. Hamlin, of Chesterfield, Va., drives Gibbs's No. 20 car in NASCAR's Grand National series.

Carl Edwards does a victory lap with the checkered flag after winning the Dickies 500 at Texas Motor Speedway. Tony Stewart remains first overall.Carl Edwards, center, celebrates with Roush Racing team members after winning the Dickies 500. Edwards moved from 4th to 3rd in the Nextel Cup standings.