Stewart kept the lead through the final set of pit stops and quickly ended runner-up Dale Earnhardt's chances of making it a duel by pulling away over the final 11 laps Sunday for his second consecutive victory.
"We're getting closer," Stewart said of the track, where he started on the pole twice this season, each time setting a qualifying record. "I feel like I've made great gains here, and I feel like (crew chief Greg Zipadelli) and the guys have made great gains here as well.
"You can't do it by yourself."
Stewart pulled away from The Intimidator to win the NAPA 500 by .672 seconds. It was his Winston Cup-leading fifth victory this year, the eighth of his career and the third time he's won back-to-back races.
Doing it this time with the black car of one of racing's fiercest competitors in the rear view mirror of Stewart's Pontiac made it better.
"He didn't get the nickname The Intimidator for nothing," Stewart said of Earnhardt, a seven-time series champion. "He's as tough as they come. ... I knew it was going to be the toughest 11 laps of my life probably."
Instead, it was much easier than the roaring crowd anticipated.
"I couldn't catch him," said a disappointed Earnhardt. "If I could have got to him, it would have been good, but I couldn't catch him."
Earnhardt outlasted Jeff Burton for second and gained 36 points on championship leader Bobby Labonte with six races left on the schedule.
"It's going to take a whole lot of gaining and a whole lot of him finishing back there," Earnhardt said of Labonte, who now leads by 213 points. "I know we didn't gain a whole lot on him today, but we gained."
Ricky Rudd finished fourth, followed by Jeff Gordon and Dale Jarrett.
Stewart, who has said all week that Martinsville isn't his favorite track, said he was spurred on by booing that lasted throughout the race.
"want to thank those three guys at the back of the grandstand," he said. "They kept booing us all day and that pumped me up more than anything."
The race seemed to be shaping up as a classic short-track event, and when the 13th and final caution flew on the 481st lap, the crowd roared because it erased Stewart's large lead and gave Earnhardt a chance.
But the green flag on lap No. 490 was a go for Stewart to win.
Labonte, who overcame a lot of bad luck to finish 10th, was happy.
"It was a good day," he said. "To come out of Martinsville 10th with everything that happened today - it could have been a lot worse."
Burton passed series champion Dale Jarrett for third, 227 points back, but left the track 60 miles from his South Boston home dejected.
"We had a great car. We had great pit stops," he said, blaming crowding on pit lane for his being beaten out of the pits at the end. "You don't have a lot of chances to win these things."
Burton appeared to have the strongest car for much of the race and led 202 of the first 467 laps. But Dave Blaney's spin brought out the 12th caution, ending 101 laps of green-flag racing and jumbled things up.
Sterling Marlin took only two tires and was first out of the pits, followed by Stewart, Gordon, Burton and Earnhardt. Stewart need only two laps to pass Marlin, Earnhardt close behind, and it never changed.
"It was a good race, and it came down to a good race at the end," Earnhardt said. "And that's what it's all about in short-track racing."
Labonte's recovery from repeated bad luck ended up being one of the biggest stories of the day, keeping him on pace for the championship.
With about 215 laps to go, all the leaders pitted under caution.
Labonte, who went onto pit road in fifth place, was on his way out when Earnhardt cut off Rudd, causing a backup that ended with Labonte getting pinched by two other cars, damaging the front of his Pontiac.
Labonte pitted twice more under the yellow to have the damage fixed, then was running 26th when it went back to green with 209 laps left.
After working his way back into the top 10, Labonte was bumped by Mike Skinner coming out of the fourth turn with 23 laps remaining.
The bump caused Labonte's car to spin in a cloud of smoke with cars passing on both sides. But he regained control and sped off, having lost just one position on the track.
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