Mediate is trying to become the 16th player to win his first start on the Champions Tour. He won six times on the PGA Tour and is probably best remembered for losing a playoff to Tiger Woods in the 2008 U.S. Open.
Mediate had five consecutive birdies on the front nine, highlighted by a drive to the green at the par-4 seventh hole. He added three more birdies after the turn and closed with a birdie at the 17th and a 10-foot eagle at the 18th.
It was the lowest round of Mediate's career, one better than his 62 at Colonial in 2001, and it snapped the tournament record of 63 set by Craig Stadler in 2007. Mediate's total of 128 through two rounds was three better than the 36-hole mark of 131 shared by Tim Simpson and Tommy Armour III.
"It has to be my best round I've played in a long time," Mediate said. "Obviously, it was my lowest. I haven't made that many putts in a long, long time. Feeling that again was cool. I haven't felt that in a while."
Pernice also had a strong day on the Old Course at Broken Sound, posting a 65 after beginning the day in a tie for the lead. He lost ground in his pursuit of his second Champions Tour title, but he said he wasn't discouraged.
"Rocco shot 61, he should be leading," said Pernice, who was the last player to win his first start on the Champions Tour in 2009. "It wasn't that easy out there.
Mediate stayed aggressive after the run of five consecutive birdies, and he said that was the key to his 61. He said he will have to continue that approach in the final round.
"You can't let down or take it off the pedal out here," he said. "You have to go crazy from the start to the finish, or you can't win. I don't know what's going to happen tomorrow, but I just want to keep putting myself in contention."
Pernice knows he won't be the crowd favorite in the final round, but he's fine with that. He even agrees with it.
"It's nice to see him playing well," Pernice said of Mediate. "He's very entertaining, a great guy and he's going to be a great addition to the tour."
Bernhard Langer, who won here in 2010, shot a 67 and is five back at 11-under 133. David Frost (65) is alone in fourth at 135.