Mediate has a two-shot lead through two rounds at the inaugural Shaw Charity Classic after firing a 7-under 64 on Saturday.
After carding two bogeys and an eagle on the front nine Saturday, Mediate reeled off seven birdies on his final nine holes.
"I didn't really play that bad on the front nine," said Mediate, who shot 29 on the back nine for the second straight day. "On the back nine, the gates they opened right up."
Through two rounds, Mediate has carded 10 birdies, two eagles and no bogeys on the final nine holes. Combined with his course record 63 he shot in the opening round, Mediate moved to 15-under 127, which is the lowest total through two rounds of any Champions Tour event this year.
"I'm going to need to go 4-, 5- or 6-under par easy to win this golf tournament tomorrow," said Mediate, who won the Allianz Championship in February in his first-ever Champions Tour start. "It's good to be where I am. I like the feeling.
"I want to go play the third round right now, but you can't do that. I just want to get to the first tee and get going."
Bobby Clampett shot 65 on Saturday to give him a two-day total of 129 to put him alone in second spot, two shots behind Mediate.
"I was just really trying to hang in there," Clampett said. "I wasn't playing particularly well early on in the round and missed a couple shots — tee shot at seven and a tee shot at nine — and managed to squeak out a couple bogeys on those holes. I just hung in there … made some good putts today."
Clampett said that fans will definitely be in for a treat on Sunday when the event's first-ever champion will emerge.
"The nice thing about the Champions Tour, you can get right there close to the action," Clampett said. "You can really sense the action. It's not an arena. You walk along literally sometimes a stone's throw away from the player. You can hear the communication sometimes between player and caddie and you're right there."
Tom Pernice Jr. carded a 67 on Saturday and sits four shots behind Mediate in a three-way tie for third place heading into the final round.
"Today was a good day to get me closer to the lead so I'm within striking distance," Pernice Jr. said. "I'm going to have to play good again tomorrow though."
Both David Frost and Michael Allen shot 66 on Saturday and sit in a tie for third place with Pernice Jr. at 11 under.
Kirk Triplett, Jay Don Blake, Jeff Sluman and Bart Bryant are in a five-way tie for fourth place at 10 under.
Blake had three eagles on his round to tie a Champions Tour record. He became the seventh golfer on the senior PGA tour to record three eagles in a single round.
Mike Goodes tied Mediate's course record with an 8-under 63 to move from a tie for 47th after the first day into a tie for 10th heading into the final round.
"I was walking down the last few holes saying if you can't have fun doing this, you can't have any fun, so I was enjoying it," said Goodes, who had eight birdies over his bogey-free round. "It was a great round and I got in position where I can have a really good tournament."
Goodes is tied with Steve Lowery, Craig Stadler and Mark Brooks at 9-under.
After shooting 69 on Friday, Fred Couples fared much better on Saturday as he fired a 6-under 65 to move into a tie for 14th spot with five other golfers.
Following a 7-under 64 on Friday, Rod Spittle of Niagara Falls, Ont., struggled by shooting a 2-over 73 to fall back into a tie for 26th place with two others at 5 under.
Dave Barr of Kelowna, B.C., fired his second straight round of even-par 71, while Victoria's Jim Rutledge shot a disappointing round of 76 to put him in second-last place overall at 7 over.