Shane Lowry of Ireland birdied four of his opening five holes Friday at the Open Championship on his way to a 4-under 67 and share of the 36-hole lead with J.B. Holmes, who had a 68.
Lee Westwood and Tommy Fleetwood are one shot behind, with Brooks Koepka and Jordan Spieth three back.
One of Lowry's best friends, Rory McIlroy, missed the cut in the first British Open in Northern Ireland since 1951, as did Tiger Woods and Phil Mickelson.
Lowry was so nervous he was shaking on the tee when the tournament began Thursday, swept up in the emotion of an Open on the Emerald Isle, and on a course he knows. He gave fans plenty to cheer when he opened his second round with three straight birdies, added a birdie on the fifth and holed a 40-foot birdie putt on No. 10 to reach 10 under, making him the only player this week to reach double figures under par. The cheers were as loud as he has heard.
"Just incredible," Lowry said. "You can't but smile, can't but laugh how it is. There's no point trying to shy away from it. It's an incredible feeling getting applauded on every green, every tee box. I'm out there giving my best, trying to do my best for everyone."
He three-putted the 14th, saved par on the next three holes with his deft touch around the greens, and closed with a bogey to fall back into a tie with Holmes, who played earlier in the day and was the first to post at 8-under 134.
Holmes won at Riviera earlier this year, and then failed to make the cut in eight of his next 12 tournaments as he battled a two-way miss off the tee and felt so bad that he never thought he'd recover. But he did enough in Detroit three weeks ago to regain some confidence, and he has been in a groove at Portrush.
"You can have that great round and that day where everything goes right. But it's nice to get two rounds in a row," Holmes said. "It shows a little consistency. And two days in a row I've hit the ball really well and putted well."
Fleetwood and Westwood, two Englishmen at different stages in their careers, each had a 67 and will play in the group ahead of Lowry and Holmes. Westwood is 46 and can make a case as the best active player without a major, considering his status -- a former No. 1 in the world and on the European Tour -- and the number of near misses in the majors, such as Muirfield and Turnberry at the Open, Torrey Pines in the U.S. Open and Augusta National, when Mickelson outplayed him in 2010.
Is it too late? Westwood wasn't willing to look that far ahead.
"There's too much ground to cover before Sunday night," Westwood said. "There's a long way to go in this tournament. I've never felt under that much pressure, to be honest. You lads write about it. I've always gone out and done my best. If it's going to happen, it's going to happen, and if it doesn't, it doesn't."
Justin Rose had a 67 and was two shots behind, along with Cameron Smith of Australia and Justin Harding of South Africa. Another shot back was a group that included Koepka, who has won three of the last six majors. He was in a tie for eighth, the 16th time in his last 17 rounds at the majors he has ended a round in the top 10.
Koepka wasn't happy with much about his 2-under 69, calling it "a little bit disappointing," perhaps because he played in dry weather and only a mild wind.
"But at the same time, I'm close enough where I play a good weekend, I'll be in good shape," he said.
Spieth hasn't quite figured out how to get the ball in play more often -- too many bunkers on Thursday, too much high grass on Friday. But the putter is not a problem, and it carried him to a collection of midrange birdie and par putts for a 67.
"I'm in contention. I feel good," Spieth said, winless since his Open title at Royal Birkdale two years ago. "I feel like if I can continue to improve each day, hit the ball better tomorrow than I did today, and better on Sunday than Saturday, then I should have a chance with how I feel on and around the greens."
Graeme McDowell, born and raised in Portrush, played well enough to make the weekend. He finished with four straight pars for a 70 to make the cut on the number at 1-over 143, and felt the pressure of sticking around for the home crowd.
The Associated Press contributed to this report.