The American carded a 9-under 62 to be 17 under at the Black Desert Resort in Ivins on Friday as Australian Cam Davis faltered and was destined to miss the cut.
Play in the second round was suspended late due to bad light with three players still on the course.
Smotherman beat his Thursday score by one shot to be one ahead of Kevin Roy (63) with fellow Americans Doug Ghim and Kevin Streelman a further shot adrift and tied for third.
The 32-year-old already had seven birdies and a bogey on his card when he reached the par-4 16th, where he converted a three metre birdie putt.
He stayed hot with the flat stick and made birdie at the par-3 17th before his two-putt birdie at the par-5 18th.
"It was just very steady — a lot of greens, a lot of fairways, a couple tight wedges," Smotherman said.
"It's what you've got to do to shoot 9 under."
Smotherman is seeking his first PGA Tour victory, along with access to the first two signature events of 2027.
The Bank of Utah Championship is the second of eight tournaments that are part of the FedEx Cup Fall, where the top 100 in the standings at the end of the year keep full cards for next year.
The top 60 are assured of getting into $20 million signature events at Pebble Beach and Riviera.
Roy is at No. 87 and would love nothing more than a good week to not worry about it.
"I think first and foremost keep a job," Roy said with a laugh.
"No, really, just keep going out and just trying to play one shot at a time and see where we stack up at the end."
Streelman, who shot a 64, needs a strong fall as he entered this week 151st in the points race.
"I feel like I have nothing to lose, really," the 47-year-old said.
"This is my almost 20th year doing this and pushing 500 starts and my family's coming in this weekend.
"I just feel I'm going to try and attack and have fun, and if things go well, great. If they don't, it's OK, too."
As well as Davis, who was tied for 69th at 5 under, other notable names to miss the projected cut of 6 under par included Maverick McNealy, Lucas Glover, and Max Greyserman all at 5 under; Tony Finau at 4 under; and Zach Johnson at 1 over.
Star rookie Jackson Koivun, fresh off his appearance on the victorious US Presidents Cup team, holed a birdie putt at 18 to shoot 67 and reach 6 under, enough to have him play the weekend.
with AP
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