Both were upstaged by Phil Mickelson yet again on Tuesday, as the left-hander shot a seven-under 64 that left him 17 under and on top of the leaderboard after the second round.

McKenzie opened on Monday with a brilliant nine-under 62 but still trailed Mickelson by one, while Pampling shot six-under on Tuesday – the joint second best score of the round – only to be headed by the five-time major winner.

As a result Mickelson, who decided to make his debut on the over-50 Tour to continue his US Open prep after he was eliminated from the PGA Tour's FedEx Cup playoffs, leads second-placed Pampling and Tom Petrovic by four.

"I've been putting really well," Mickelson said. "Today I didn't drive it the way I've been driving it. I kind of a hung a few drives, so I'm going to the range and try to work on that now.

“When I come out tomorrow, I'll try to be a little bit more aggressive with the driver and see if I can make a few more birdies.” – Phil Mickelson

"But when I come out tomorrow, I'll try to be a little bit more aggressive with the driver and see if I can make a few more birdies."

A few more? He's already made 19 of them in his first 36 holes.

Mickelson could still squander the lead in the final round Wednesday, when tee times were moved to the early morning because of expected bad weather in the afternoon.

But given the quality of his short game through 36 holes, the more pressing question is whether he could break the PGA Tour Champions' 54-hole scoring record of 191 – shared by Bruce Fleisher, Loren Roberts, Bernhard Langer, David Frost and Rocco Mediate.

Mickelson would need to shoot 65 in his final round Wednesday to move atop the list.

Petrovic and Pampling each shot 64-65 over the first two rounds.

McKenzie is tied for sixth and seven behind Mickelson after posting a one-under second round.