LOUDON, N.H. — Blame the tough racetrack, the Car of Tomorrow or simply circumstance. Whatever the reason, there have been no repeat winners in the last four years of NASCAR Sprint Cup racing at New Hampshire Motor Speedway.

If that trend holds, Greg Biffle, who won here in September, won’t be in Victory Lane on Sunday.

Nor will Kurt Busch, Clint Bowyer, Denny Hamlin, Kevin Harvick, Kyle Busch, Ryan Newman or Tony Stewart.

That impressive group of drivers includes the last eight Cup winners on the 1.058-mile New Hampshire oval.

No repeats.

The trend is even more extensive in the Nationwide Series, which had 22 different winners in 22 races heading into Saturday’s Camping World 200.

“Certainly, this racetrack is one of the harder flat tracks that we go to,” Biffle said. “It’s really, really flat, and I think that it changes a lot, and the guy that hits it just right that weekend is why you see different winners all the time with no repeat winners.

“Hopefully, we’ll break that trend this weekend. We’ll just have to wait and see.”

Stewart started the Cup string when he won the summer race in July 2005. Jeff Gordon, Jeff Burton, Jimmie Johnson and Busch all won multiple races here before that, including season sweeps by Johnson in 2003 and Busch in 2004.

Since then, though, no repeaters.

Busch said at least part of the explanation is the Car of Tomorrow, which began competing on NASCAR’s shorter tracks in 2007.

“You can say that the new car has added a different twist because we continually come back to the racetracks that we’ve seen before with completely different setups and that will create different winners and a trend such as that,” Busch said.

“This racetrack has a lot to do with pit strategy. Once you get towards the end, you want to pit and stay out as long as you can and, sometimes, guys who haven’t been running well all day will stay out and try to stretch their fuel and they end up having track position,” added Busch, who won a rain-shortened race here last June. “Timely yellows come out, and so it creates a road course-type atmosphere where you pit as soon as you can make it to the end and then stay out and hang on.”

Stewart, who also won here in July 2000, said he has no idea why there has been a string of different winners in New Hampshire.

“I think every year this track changes a little bit and every year everybody gets a little bit better on what it takes to be good here,” said Stewart, the series points leader who will start from the pole in Sunday’s Lenox Industrial Tools 301. “This is a unique place and I think that’s the reason guys every year kind of hit it or miss it.”

Assuming the trend holds, keep an eye on Mark Martin, who won on the one-mile oval at Phoenix earlier this year and brings the same car to New Hampshire.

“This is a tough race track,” said Martin, who has never won at NHMS. “It’s kind of tough to pass on and it’s tight quarters and it’s like an expanded version of Martinsville in some ways. So it can be fun if your car is really good. But, if your car is not really good, it can sure be a challenge racing around the middle of the pack.”

Hamlin’s car was really good when he won at New Hampshire in July 2007 and he’s among several drivers hoping to end the streak of different winners on Sunday.

“I know we’ve had a lot of success here each time we’ve been here, but we’ve been here with a different setup every single time,” Hamlin said. “It’s just a real hard track to kind of perfect and get right.

“I think the drivers can make up for a little bit, but ... I don’t think we’ve got it figured out on the car side yet. I don’t think anyone has.”