Spieth has pieced together rounds of 66 and 65 to hit 13-under and Scott is on that same number after playing his final seven holes in a staggering 8-under on Friday.
They share second place with American Harry Higgs and Korean Seonghyeon Kim.
And yet despite the flurry of birdies and eagles from that quartet, they're still a hefty five shots behind runaway leader Keith Mitchell.
Mitchell has made an extraordinary start. He blasted a 10-under 62 in round one and backed that up with a 64 on his second lap to reach 18-under.
Five-shot leads on the PGA Tour are rare: just 22 players have led a regular event by five strokes at halfway since 1996 and 17 of them went on to win.
Using that stat, Mitchell's odds to win look generous. It's tempting to look elsewhere for more exciting prices but the best one could be right under our noses.
But if Mitchell slips, this Vegas showdown remains an absolute crapshoot.
Here are the best stats, quotes and social from The Summit Club after 36 holes.
Stats and facts
This is Mitchell's second 36-hole lead/co-lead on the PGA Tour. He converted the other when winning the 2019 Honda Classic.
Mitchell leads the field in Strokes Gained: Putting (7.781). He made a total of 143'10" of putts in round two.
Spieth ranks 4th for SG: Tee To Green and 20th in SG: Putting
Scott finished birdie-birdie-eagle-birdie-par-birdie-eagle to post his second-round 63. He made a 3'1" putt for eagle on the par-5 14th hole and a 4'11" putt for eagle on the par-5 18th.
Scott had a career-best 14 one-putt holes during his second-round 63.
Keith Mitchell (-18, 64)
"I'm definitely excited and pleased. I spent a lot of time in the last few days leading up to this tournament working hard on my game and it's showing. I'm very thankful for that.
"Just shows you that hard work pays off as long as you're doing the right things. My putter's definitely been nice and my speed has been a lot better this week. If those two things stay through this weekend, hopefully I can keep hitting in some quality shots and capitalising.
"Definitely going to be different tomorrow, probably have a little bit more wind, a little bit more bumps on the greens but just try to take advantage of a nice, hot putter."
Jordan Spieth (-13, 65)
"I like wind, I like knowing where the wind is. I'd rather play in 15 to 20 out here than light and variable. It's just harder for me to commit. I just grew up in wind almost every day.
"I told [caddie] Michael coming in, I said I don't think this is the best setup for me, especially I really haven't practised much at all. Took a week off and then just played a couple rounds the next week.
"So I was kind of coming in here being like, all right, let's play one this fall and this happens to be the one. And now I feel good about the progress since I've been here this week and the course could be for me if I want it to be, I guess, on the weekend."
Adam Scott (-13, 63)
"I've been playing well and, you know, you can't expect a finish like that, but I'm going to take it. I hit a lot of shots close and that made light work with the putter.
"You know, kind of put myself in contention. I mean, I'm a long way back still, but 36 holes to go, I like where I'm at, moving in the right direction.
"There are a lot of birdies out there. Hopefully I can get it going a bit more on the front nine. A fast start would do the momentum a world of good for the weekend."
Rickie Fowler (-12, 66)
"I'm definitely happy with it. I left some out there the last two days, but also feel like I've taken advantage of some opportunities as well. So definitely happy with the first two days, like where I'm at, and definitely heading in the right direction.
"The goal right now is to go win. I know I can play well on this golf course, I've proven that the first two days, but we're still a ways back so I need to play a solid round of golf tomorrow to give myself a legitimate chance."
Abraham Ancer (-9, 65)
(On his albatross) "I was in between flying it there on the green with a longer club or just hitting like that 4-iron just a little bit lower, make sure it lands somewhere short of the green and chase it up there just because I know long was probably not a good spot to be there.
"Yeah, just throwing it out there to the right, let it feed and just try to get lucky. Thankfully, I did. A lot of things have to go right for that ball to go in and it looks really cool on video, too."
Abraham's albatross, Im's near miss, Scott's red-hot finish from sand, Team Mav and Rose reads it perfectly
Triple A: Abraham Ancer albatross!
Im nearly adds another!
Up and down from sand for Scott - from 229 yards!
Some local support for Maverick
Rose's perfect pitch