As well as Spieth, Kuchar and McIlroy, only six other players are under par for the championship.
"But we really haven't played this course in good weather".
After going five over through six holes in his opening round, Rory McIlroy got to one under for the championship by the end of his second to move into contention.
With 20mph winds and steady rain blowing across the hole, the two-time major winner's celebratory start quickly turned into a horror show as he appeared to lose his hold on a wet grip and his tee shot flew straight right and our-of-bounds.
But McIlroy made a double bogey on the 10th hole and was at 1 under.
The game is now officially on for the world's former No. 1 player.
There were dropped shots at 13 and 15 but a birdie at the long 17th helped complete a largely satisfactory day for the world number four.
He explained: "I think [the 12th] was playing about 162 yards".
"There was a lot of quality out there and I was happy to see that". But then you've got to play and make a score.
Spieth, the World No 3, avoided the grim early-morning conditions on the Southport links as he went out with reigning champion Henrik Stenson and promptly fired a flawless round featuring five birdies and not a single dropped shot.
"I thought this is a flawless tune-up for coming into this week".
Despite McIlroy's signs of life, the sternest challenge to Spieth will come from U.S. Open victor Koepka.
When he realized he made the cut by one stroke he was understandably excited.
His advantage was back to one after a bogey on 14, but a bounce-back eagle extended his lead to three before a three-putt bogey on 16 gave his chasers hope. Ian Poulter and Brooks Koepka are on three-under, Scotland's Richie Ramsay is on two-under and Austin Connelly, Gary Woodland and Richard Bland are level with McIlroy on one-under. This course has a lot of crosswinds, so it's tough to judge how far the ball is going to fly depending on what shot you play.
Mark O'Meara was supposed to hit the first tee shot to start the 146th British Open. That was really the only thing that at Muirfield (The Memorial), and at the U.S. Open, I mean it was really just putting. Past success at a course can always bring confidence to a player.