Houston couldn't find a flow on offense early and fell behind by 12 against the typically slow-starting Bobcats.
Harden was just 2 of 9 from the field in the first half and missed several easy shots, including a pair of driving layups. He also had three turnovers, including one where he inexplicably lost control of his dribble with no defender near him. He twice had his shot blocked in the first half.
Harden's shaky first half ended when his heave from half-court as time expired sailed about 10 feet wide of the backboard.
Meanwhile, Walker was just getting started.
He made all three 3-point attempts in the first half, helping the Bobcats take a 56-45 lead at the break. And Charlotte led by seven entering the fourth quarter after Walker knocked down two more 3s late in the third quarter.
"He was just killing us," McHale said.
But as has been the problem most of the season, Charlotte had trouble closing out an opponent, shooting just 4 of 19 in the fourth quarter and scoring just 13 points.
Walker had seven of those points and Sessions had six, but no other Bobcats scored in the final period.
"Kemba and Sessions got going but we really need that third scorer," Bobcats coach Mike Dunlap said. "It's not an individual on our team, it's just finding who that third scorer is."
Walker said he's been working overtime on his jumper of late, but didn't feel much like talking about his career high after the game.
He was still miffed at yet another blown lead at home.
"It's tough," Walker said. "We're trying our hardest to win these games, but it's just not working out right now. Hopefully, things will work out for us. It gets tough in the fourth quarter. Teams adjust to what we've been doing. You have to execute. I thought we got some pretty good shots and just missed them."
NOTES: Bismack Biyombo tied a career high with seven blocked shots, four of those on Harden. ... Walker's six 3-pointers were a career best. ... Harden has scored at least 20 points in a career-high 23 straight games. ... Patrick Beverly scored a career-high 10 points for the Rockets.