Rai, a two-time winner on the DP World Tour chasing his first PGA title, fired a seven-under-par 65 to stand on 13-under 131 after 36 holes at Detroit Golf Club.
That left the 29-year-old from Wolverhampton level with Bhatia, who shot 67 to put him on 131 without a bogey this week.
"Felt like I drove it pretty well," Rai said. "Hit a lot of good approach shots. Felt like I hit a lot of greens. I gave myself a lot of looks and nice to finish off that way on 17 and 18."
Rai, who had five-foot birdie putts at the third and par-3 11th holes, reeled off three birdies in a row to close the front nine.
He drove the par-5 17th in two to set up a tap-in birdie and sank a birdie putt at 18 from just outside 20 feet to seize a share of the halfway lead.
"The game is in a good place," Rai said. "Striking it well tee to green. It's nice to see a few putts go in over the last couple of days.
"It has definitely given me a little more confidence on the greens the last couple days which has made a difference."
Americans Troy Merritt, Cameron Young and Taylor Montgomery shared third on 131 with South African Erik van Rooyen.
Bhatia won playoffs to capture both his PGA titles, at last July's Barracuda Championship and last April's Texas Open.
Back-nine starter Bhatia sank a three-footer to birdie the 10th hole then rolled in a birdie putt from just over 30 feet at the par-3 15th.
He added back-to-back birdie putts on 18 from four feet and the first hole from three feet then tapped in for birdie at the par-5 seventh after reaching the green in two.
"It's nice to get a score like what I had today," Bhatia said. "It's a fun play."
His craziest shot of the day was off the 17th tee when his ball rolled into a small drain hole.
"That was wild. No, never seen it. Rules official has never seen it, so it was kind of one in a million chance that ball goes in that small hole in that drain, so it was pretty funny," Bhatia said. "That was hilarious."
American Joe Highsmith, who missed the cut in his past five PGA starts, aced the par-3 fifth hole, his 14th hole of the round. He shot 64 to stand on 135.
American Neal Shipley, low amateur at the Masters and US Open, stood on 135 in his professional debut.
US 15-year-old amateur Miles Russell made his PGA Tour debut, going 74 and 70 to miss the cut.
