Henrik Stenson produced a brilliant second round 65 to sit just one shot off the lead at the The 145th Open Championship.
Overnight leader Phil Mickelson came into day two with a three-shot advantage and had increased that to five as he reached the turn in 33 with heavy rain and increasing winds arriving at Royal Troon.
The 2013 champion gave a shot back on the back nine, though, and Stenson - who had also turned in 33 - made three birdies on the way home to get to nine under and cut the gap to one.
Stenson and Mickelson occupied the top two spots on the leaderboard at Muirfield in 2013 as the American claimed his most recent win on the European Tour and they are set to do battle once more over the weekend.
Søren Kjeldsen was then at seven under after a bogey-free 68 alongside 2011 US PGA Championship winner Keegan Bradley, with defending champion Zach Johnson at five under.
England's Andrew Johnston was leading the home challenge a shot further back along with Sergio Garcia, Charl Schwartzel, Tony Finau and Bill Haas.
Scott Hend was the man making a big move out of the later starters, the True Thailand Classic Presented by Chang winner was also at four under after picking up four shots in his first seven holes.
Mickelson, following on from a course-record 63 on Thursday, took advantage of the par five fourth and then put his approach on the seventh to four feet before nearly spinning the ball back into the hole on the Postage Stamp for an ace.
At that point he had a five-shot lead but he blemished his card for the first time this week at the 12th before hitting back with a 20-foot putt on the 14th.
Another shot was dropped on the next and while he looked in big trouble in the bunker on the 17th, Mickelson produced an exquisite save and parred the last for a 69.
Stenson caught fire early, making three straight birdies from the third and adding another on the seventh. A shot went on the ninth but further birdies on the tenth, 13th and 16th meant the Swede had cut the gap to one.
Kjeldsen has been a picture of consistency this season, missing just one cut and he achieved a seventh-placed finish at the Masters Tournament in April.
That consistency shone through with birdies on the par five fourth and sixth, two excellent par saves on the seventh and 11th and a huge birdie putt on 17th.
Schwartzel fired a 66 to sit alongside Johnston, who had seven birdies, two bogeys and a triple in a rollercoaster second consecutive 69. Garcia three-putted the last in a disappointing finish in his 70.
World Number Four Rory McIlroy was in the group at three under after four holes of his second round, five shots clear of Masters Tournament winner Danny Willett who was battling to make the cut.
