TROON, Scotland — This was the kind of day Phil Mickelson rarely gets at home, golf against the elements, when a cool head and a dry grip are no less important than a consistent swing. The kind of day — classic Scotland, wind and rain — that Mickelson, a California kid, said he relishes.

It was the kind of day — gray, gloomy and mainly wet — that Soren Kjeldsen has experienced during much of his golfing life in his native Denmark. “I’m used to playing in bad weather,’’ he said. “You don’t stay inside, because you miss too many days.”

The only thing anyone missed Friday in the second round of the 145th British Open was sunshine.

Mickelson persevered after his record-tying first-round 63, shooting a 2-under-par 69 at Royal Troon for a 10-under 132, a 36-hole Open record at Troon.

That left him a shot ahead of Henrik Stenson, who had the best round of the day, a 6-under 65 for 133. Two back at 7-under 135 and tied for third are Kjeldsen (68) and 2011 PGA champion Keegan Bradley (68). Last year’s Open winner, Zach Johnson, shot 70 and is fifth at 137.

The Big Four? They weren’t exactly big busts, nor were they particularly sharp.

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Dustin Johnson is 2 under after shooting 71-69 and Rory McIlroy shot 69-71. Jason Day had 73-70 for 143 and Jordan Spieth shot 71-75 for a 146, which, phew, was right on the cut line. “Just tried to smile,” Spieth said, “tried to enjoy the fact you don’t play in this [weather] too often.”

Mickelson is 46, Stenson is 40 and Kjeldsen is 41. When Mickelson won the Open three years ago at Muirfield, Stenson was second. Those guys have been around the green a few times.

“I understand the age thing,” said Mickelson, who if he holds the lead will be the oldest winner since 1867, when the champion was “Old” Tom Morris, who was 46 years, 102 days old. When the Claret Jug is awarded Sunday, Mickelson will be 46 years, 31 days.

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“The fact is from 10 years ago, when I was playing my best golf, I’m 25 pounds lighter,” he said. “I’m in better shape. So I don’t see any reason why I can’t continue not just this week but for years. That’s kind of what the game plan is.”

His plan Friday was to slop around. While fans huddled under umbrellas, Mickelson and the pros splashed toward their goal, some not as merrily as Phil.

Asked if he would play in similar conditions at home, where it hardly ever rains, he said, “Yeah. I would love it because in San Diego, we get maybe three days like this a year, and on those days, there’s nobody on the golf course. So those are my favorite times.”

Stenson was happy that he gained four shots on Mickelson and is eager to get that first major. “There’s been two or three I’ve been up there,” he said. “Muirfield, the PGA at Valhalla. If things had gone my way, I’m sure I could have had one or two. But not to this date.”

While Mickelson, Stenson and Kjeldsen found satisfaction in the damp, others did not. Ben Curtis, the 2003 Open winner, went into three bunkers on the par-4 third hole, took a 10 and shot 83. Martin Kaymer, tied for second going into Friday after a 66, had a triple-bogey 7 on 10, shot 73 and fell into a tie for 11th.