ARDMORE, Pa. — Phil Mickelson began his week with a flight back-and-forth across the country. Even longer might be the 18 holes that now stand between him and that U.S. Open title he has been chasing his entire career.

And he’s never had a better opportunity than this one.

Despite a bogey on the final hole of a taxing Saturday afternoon, Mickelson was the sole survivor to par at Merion with an even-par 70 that gave him a one-shot lead over Hunter Mahan, Charl Schwartzel and Steve Stricker going into the last round.

It’s the first time Mickelson has held the outright lead through 54 holes in the U.S. Open, and the timing could be right.

Mickelson celebrates his 43rd birthday Sunday — on Father’s Day, no less. He left Merion on Monday and didn’t return until three hours before his tee time on Thursday so he could attend the eighth-grade graduation of his oldest daughter.

“It’s got the makings to be something special,” Mickelson said. “But I still have to go out and perform, and play some of my best golf.”

Mickelson, who already has a record five silver medals for being runner-up at this demanding major, was at 1-under 209.

And the fun is just getting started.

“It’s a hard challenge, but it’s a lot of fun,” Mickelson said. “Every shot requires such great focus because a penalty can bite you quickly. I can’t wait to get back and playing. I feel good ball-striking, I feel good on the greens. I think it’s going to take an under-par round tomorrow.”

Saturday was more about weeding out the pretenders for this U.S. Open — and one of them turned out to be Tiger Woods. He started out just four shots out of the lead, and made a bending, 12-foot birdie putt on the opening hole.

It never got any better for the world’s No. 1 player. He made seven bogeys the rest of the way and didn’t add another birdie, matching his worst U.S. Open score as a pro with a 6-over 76.

Woods was 10 shots behind.

The final hour might have been a sneak preview for Sunday. At one point, there were five players under par, and suddenly there was only Mickelson.

Luke Donald had the outright lead until two bad swings on the last two holes — a 2-iron into the bunker on the 17th that led to bogey, and another 2-iron into ankle-deep rough well right of the 18th green that led to a double bogey. Just like that, one of the best rounds of the day turned into a 71, and he was two shots behind.

Hunter Mahan let his spectacular back nine filled with four birdies go to waste with a bogey-bogey finish for a 69. He will be in the final group for the first time in a major with Mickelson, whom he considers a close friend.

The third round featured so much movement, and so many wild swings, that seven players had a share of the lead at some point. Even though USGA executive director Mike Davis said the course was set up to allow for good scores, this was more about hanging on for dear life.

Thirty players were separated by only five shots at the start of the third round. By the end of the day, there were just 10 players separated by five shots, including amateur Michael Kim. He was tied for third until losing four shots on the last three holes.