His third-day sack of bass gave Chapman a total of 59-14, but he said he was a bit worried with the falling weights his spots yielded today.
"I backed off that spot yesterday, and I hope that doesn't come back to haunt me," Chapman said.
Joining Chapman in the tournament's finale will be South Carolina's Marty Robinson (58-9), Alabama's Timmy Horton (58-1), Mississippi's Cliff Pace (57-2) and Alabama's Matt Herren (56-11).
Gonzale's Greg Hackney goes into the final day of competition in sixth with a total of 55-3.
Chapman said he has continued to fish a single point that tapers off into deep water, with the fish holding in about 25 feet — just north of the thermocline.
"I haven't caught a fish shallower than 25 feet," he said. "I can cast the whole area from one spot."
He said he fished clean again today, putting every fish that bite into the boat. However, he said he got about half the bites as the point yielded the first two days.
"I caught 20 fish the first and second days, but today I only got 10 bites," Chapman said. "Today was quite a bit tougher."
All but one of the fish came on a spoon, he said.
Second-place Robinson put 21-5 on the scales today from an area in the northern portion of the lake, and catching his fish quite a bit shallower than most of the other pros.
"They're from 10 to 14 feet deep," he said.
He caught his limit on jig, working the lure down a contour change.
Once the bass stop feeding, he said he has to work harder to make them bite.
"It's a reaction bite if they're not feeding," Robinson said. "You might have to pull up into something and pop it out to make them bite."
Horton jumped from 21st to third on the strength of a 27-pound, 9-ounce sack anchored by a monster that went an ounce shy of 16 pounds. That third-day stringer represented almost half of his three-day total.
"It was special," he said. "It was every cast for an hour."
All of his first limit of fish came off a Bomber Fat Free Shad BD8 crankbait in 19 to 20 feet of water.
He caught about 23 pounds of the stringer in the southern portion of the lake early in the morning, but after having to run to the landing to change out batteries he decided to gamble on catching a kicker 40 miles upstream on a spot he'd caught one good fish a day during the previous two days of fishing.
"It's a little bit of rough bottom, some gravel, in about 15 feet of water," Horton said. "When you get in that gravel, you get one bit, but it's a bit one."
The kicker fell for a Carolina-rigged 10-inch Yum worm.
Gonzales' Hackney put his heaviest sack - 20 pounds, 9 ounces — today, and said it was a hectic bite while it lasted.
"I got eight bites on eight casts," he said. "It's a reaction bite; I'm dropping a bomb on them."
And he's having to make pinpoint casts to catch them, even though he's in 17 to 25 feet of water.
"They're in little bitty spots, the size of the back of that truck," Hackney said.
But he said the fish are bunched up in strange groupings.
"One cast you can catch a 12 incher and the next cast you can catch a 12-pounder," Hackney said. "They're wadded up together."
The field is cut to the top 12 for tomorrow's final day, with the winner walking away with the $100,000 check and an automatic berth in the 2013 Bassmaster Classic.