Gilder, the overnight leader, shot a 5-under 67 on Saturday to reach 13-under-par 131 through two rounds. That was good enough to equal the 36-hole tournament record and gave Gilder a two-shot lead over Morris Hatalsky (64) and D.A. Weibring (66).
But seven other players are within five strokes heading into Sunday's finish.
Among them are Tom Watson, a seven-time winner on the Champions Tour and 39- time champion on the PGA Tour, and Curtis Strange, who claimed 17 titles on the PGA Tour but has yet to win on the senior circuit.
Watson (68), who is the only player in the field still without a bogey, and Strange (66) are at minus-10.
'There's a lot of guys playing well here and the golf course is susceptible to a lot of birdies,' said Gilder, who tied a course record with his 64 in the first round.
'These guys are going to be coming from everywhere, so I'm going to have to play good, I'm going to have to play steady and try not to make any mistakes.'
The last of Gilder's seven Champions Tour titles came at the 2003 Emerald Classic. He hasn't finished higher that a tie for fourth place this year, and that came at the Allianz Championship in June.
Since then, the 54-year-old hasn't placed better than his tie for 12th at the U.S. Senior Open Championship.
'It feels really good,' Gilder said of being in the lead. 'I felt very good today -- not nervous at all and I felt like I was under control most of the time.'
Gilder opened his round with birdies on three of his first five holes to reach minus-11. He stumbled to his only bogey of the day at the par-4 sixth, but got that stroke right back with a birdie at No. 7 to make the turn at 11 under.
After a string of eight straight pars, he moved further into red numbers with birdies at the 16th and 18th, his fifth and sixth of the day. Weibring had been keeping pace with Gilder, but he missed a short par putt at the 18th to fall back.
'It should be a good shootout tomorrow,' said Weibring. 'You'll need to make lots of birdies to win. Bob's played great for two days.'
Also within striking distance of Gilder is Bruce Fleisher, who is in sixth place at 9 under after a second-round 66. Pete Oakley (67), Hajime Meshiai (69) and former major league pitcher Rick Rhoden (68) share seventh place, one stroke further back.
All in all, 58 players are even-par or better in the 77-player field.