Fourth-ranked Jon Rahm endured a frustrating day on the greens, but his four-under-par 68 was enough to hold off rookie Davis Thompson and claim a second US PGA Tour title in as many weeks at the American Express tournament.
Spain's Rahm, who opened the year with a victory in the Tournament of Champions in Hawaii, had five birdies on the Stadium Course in La Quinta, California, finishing with a 27-under-par total of 261.
Thompson, who started the day tied with Rahm for the lead, carded a three-under 69 for 262.
"Ball-striking was great, I hit a lot of great putts -- it's just golf," Rahm said of a multitude of putts that didn't drop. "I was burning edges all day."
Rahm led much of the day after back-to-back birdies at the first and second -- both from about two feet. He rolled in a seven-foot birdie at the ninth and picked up another stroke at 11 -- but it was far from smooth sailing from there.
A bogey at 13, where he missed the green and his five-foot putt to save par lipped out, Rahm was tied with Thompson for the lead.
He got his nose in front again with a birdie at the par-five 16th, where his second shot from the fairway avoided a steep drop off to a greenside bunker and his eight-foot birdie putt agonizingly circled the cup before falling in.
Thompson, meanwhile, was in a tough lie in a fairway bunker on the way to a par at 16.
"The turning point was 16," Rahm said. "He missed that tee shot and I put it in the fairway. That's pretty much a half-stroke penalty right there.
"I knew if I did what I could do I was mostly likely going to have a one-shot lead going to the last two holes."
Thompson, a former amateur standout at the University of Georgia and a winner on the Korn Ferry developmental tour, had followed his first birdie of the day at the fourth with a bogey at the fifth, where he was in the water.
He closed the gap to one stroke with birdies at the sixth, ninth and 11th.
- 'What if?' -
He came agonizingly close to pulling level again at the 17th, where his 48-foot birdie putt brushed the pin and didn't drop.
"I usually always leave the stick in from a long distance," Thompson said. "I feel like it helps me with my speed. I'll probably play the 'what if' game in my head for a long time, unfortunately."
Rahm then saw his 20-foot birdie attempt at 17 settle on the edge. and he was in a fairway bunker off the tee at 18 while Thompson found the fairway.
But Thompson's second shot went through the green, leaving him a tough chip from a swale below the putting surface while Rahm found the green for a routine par to win.
"Luckily, it was enough," Rahm said.
Despite the disappointment, Thompson called it a "great week" in the California desert, where his five eagles in the first two rounds matched the PGA Tour record for a 72-hole tournament.
"A lot of nerves and I hit a lot of quality golf shots under pressure, which was really cool," he said.
Xander Schauffele and Chris Kirk shared third on 263. Schauffele's 62 included an albatross at the par-five fifth -- where he holed his second shot from 225 yards out in the fairway.
Kirk closed with a 64.
Second-ranked Masters champion Scottie Scheffler, who needed a solo ninth-placed finish or better to supplant Rory McIlroy atop the rankings, carded a 65 for a 22-under total of 266 that left him tied for 11th.