INDIANAPOLIS — JR Hildebrand was one turn away from winning the Indianapolis 500 and within sight of the checkered flag when the 23-year-old rookie made the ultimate mistake.

Leading by almost 4 seconds with a lap to go, Hildebrand skidded high into the wall on the final turn, and Dan Wheldon drove past to claim an improbable second Indy 500 win Sunday in his first race of the year.

“It’s a helpless feeling,” Hildebrand said.

Wheldon, the 2005 winner but without a full-time ride this season, appeared headed for his third straight runner-up finish when Hildebrand took the white flag needing only to make it through the last of 200 laps around the 2½-mile speedway.

The first three turns went smoothly. Then Hildebrand came up on another rookie, Charlie Kimball, in the fourth turn. Instead of backing off, Hildebrand moved to the outside to make the pass and lost control, slamming the wall to a collective gasp from the crowd of 250,000.

“I caught him in the wrong piece of track,” Hildebrand said. “I got up in the marbles and that was it.”

Hildebrand’s crumpled machine slid across the finish line, still hugging the wall, in second place. While Wheldon celebrated, IndyCar officials reviewed the video to see if Wheldon passed the wrecked machine before the caution lights went on. He clearly did, and Hildebrand’s team, Panther Racing, said it would not protest.

“I just felt a lot of relief. It’s an incredible feeling,” Wheldon said. “I never gave up.”

He took the traditional swig of milk and headed off on a triumphant lap around the speedway — a lap that Hildebrand should have been taking.

Instead, the youngster stopped by the garage to get a look at his mangled car, which was hauled through Gasoline Alley instead of being wheeled into Victory Lane. He’s now in the company of athletes such as Jean Van de Velde, who squandered a three-shot lead on the 72nd hole of the 1999 British Open, and Lindsey Jacobellis, whose wipeout at the 2006 Winter Olympics cost her a certain gold medal.

They had it in the bag — then threw it all away.

“I’m just frustrated. It’s not because we came in here with the expectation of winning and we didn’t,” Hildebrand said. “I felt like I just made a mistake and it cost our boys. I guess that’s why rookies don’t win the Indianapolis 500 a whole lot and we’ll be back next year, I guess.”

The 100th anniversary of America’s most famous race was dominated much of the day by Chip Ganassi’s top two drivers, defending champ Dario Franchitti and 2008 winner Scott Dixon.

But after a series of late pit stops, things really got interesting. Second-generation racer Graham Rahal spent some time up front. Danica Patrick claimed the lead but was had to stop for fuel with nine laps to go. Belgium driver Bertrand Baguette had already gotten past Patrick, but he didn’t have enough fuel, either.

When Baguette went to the pits with three laps to go, the lead belonged to Hildebrand. All he had to do was make it to the end.

He came up one turn short.

“My disappointment is for the team,” Hildebrand said. “We should’ve won the race.”

Not that Wheldon isn’t a deserving champ. Despite plenty of success in his IndyCar career, he lost his ride at Panther Racing — where he was replaced by Hildebrand, no less — and couldn’t find a regular job this season.

He sat out the first four races of the year, then picked up a one-race deal with Bryan Herta Autosport. Surely, Wheldon will be able to find a better gig now after beating Hildebrand by 2.1 seconds with an average speed of 170.265 mph.

“Dan Wheldon, he’s a great winner,” Patrick said. “And what a great story. He hasn’t run this year. ... That’s really cool.”

Still, it was a bitter disappointment for Patrick, who ended up 10th.

“It’s more and more depressing when I don’t win the race,” said Indy’s leading lady.

Wheldon never led a lap until the last one, the first time that’s happened since Joe Dawson won the second Indy 500 in 1912.

It was the second time a driver lost the lead on the last lap — it happened to another rookie, Marco Andretti, in 2006 — and it’s something Hildebrand will always remember.

“Is it a move I would do again?” he said. “No.”

Rahal finished third, followed by hard-charging Tony Kanaan, who came all the way from the 22nd starting spot to contend for his first 500 win. Dixon was fifth, followed by Oriol Servia, while Franchitti lost speed in the closing laps and slipped all the way to 12th.

Indianapolis 500

Sunday

At Indianapolis Motor Speedway

Indianapolis

Lap length: 2.5 miles

(Starting position in parentheses)

All cars Dallara chassis, Honda engine

1. (6) Dan Wheldon, 200 laps.

2. (12) J.R. Hildebrand, 200.

3. (29) Graham Rahal, 200.

4. (22) Tony Kanaan, 200.

5. (2) Scott Dixon, 200.

6. (3) Oriol Servia, 200.

7. (14) Bertrand Baguette, 200.

8. (21) Tomas Scheckter, 200.

9. (27) Marco Andretti, 200.

10. (25) Danica Patrick, 200.

11. (8) Ed Carpenter, 200.

12. (9) Dario Franchitti, 200.

13. (28) Charlie Kimball, 199.

14. (5) Will Power, 199.

15. (11) Vitor Meira, 199.

16. (19) Justin Wilson, 199.

17. (16) Helio Castroneves, 199.

18. (7) Buddy Rice, 198.

19. (30) Alex Lloyd, 198.

20. (31) Pippa Mann, 198.

21. (32) Ana Beatriz, 197.

22. (17) John Andretti, 197.

23. (33) Ryan Hunter-Reay, 197.

24. (15) Davey Hamilton, 193.

25. (24) Paul Tracy, 175.

26. (4) Townsend Bell, 157, Contact.

27. (26) Ryan Briscoe, 157, Contact.

28. (1) Alex Tagliani, 147, Contact.

29. (13) James Hinchcliffe, 99, Contact.

30. (20) Jay Howard, 60, Contact.

31. (23) Simona de Silvestro, 44, Handling.

32. (18) E.J. Viso, 27, Contact.

33. (10) Takuma Sato, 20, Contact.

Race Statistics

Winner’s average speed: 170.265 mph.

Time of Race: 2 hours, 56 minutes, 11.7267 seconds.

Margin of Victory: Under caution.

Cautions: 7 for 40 laps.

Lead Changes: 23 among 10 drivers.

Lap Leaders: Dixon 1-7, Tagliani 8-26, Dixon 27-33, Tagliani 34, Dixon 35-60, Franchitti 61, Carpenter 62-64, Franchitti 65-72, Dixon 73-98, Franchitti 99, Hildebrand 100-103, Franchitti 104-112, Servia 113-128, Franchitti 129-137, Hildebrand 138, Baguette 139-140, Franchitti 141-163, Servia 164-165, Rahal 166-171, Dixon 172-178, Patrick 179-188, Baguette 189-197, Hildebrand 198-199, Wheldon 200.

Points: Power 194, Franchitti 178, Servia 150, Kanaan 135, Dixon 129, Rahal 120, Briscoe 114, Hildebrand 113, Tagliani 110, Conway 102.