Mickelson made 16 birdies and an eagle during the first two days in the desert
Phil Mickelson followed his career – the best 60 with a four under 68 to keep a lead of two shots halfway round two in the Desert Classic in California.
The 48-year-old, three away at night after his 10 birdies and an eagle at La Quinta, had a double bogey in round two at the Nicklaus Tournament Course.
But he birdied four of the last five holes for a 16 under half total.
On Saturday he plays the third location of the event, the stadium course, which also organizes the last round of Sunday.
Mickelson started his round on the 10th and birdied his second and third hole.
The double bogey came to his ninth hole, but he ended in style with a beautifully controlled pitch turning back to five feet at the last for his sixth birdie of the day.
Asked to compare his second round with his 60, the American said: "I actually felt better hitting, but I did not do very well compared yesterday, where I was making everything."
During his round, the left hander was about to take a drop using the time-honored method of shoulder height, but an official rule was present to remind him that – from 1 January – the the knee had to be done, and that no punishment was imposed.
The last time Mickelson took the lead halfway through the tournament was during the 2016 Open when he went through to runner-up of Henrik Stenson.
"This was a nice, perhaps startling start for me and it's nice to be in the mix," he added.