Undeterred by a weather delay that created gusting wind midway through her round, Bader shot a 6-under 66 on Friday to take a one-shot lead over Young Kim (64) after two rounds at the LPGA Corning Classic.
Bader finished at 13-under 131 to tie the 36-hole tournament record set three years ago by Michelle Estil.
Paula Creamer (68) was third at 10 under, one shot ahead of Mi Hyun Kim (67) and Becky Morgan (66). Natalie Gulbis (67), Jamie Hullett (70), Diana D'Alessio (69), In-Kyung Kim (69), and Jean Bartholomew (68) were 8 under, and first-round leader Charlotta Sorenstam (73), Japan's Ai Miyazato (69), and Alena Sharp (63) were among seven players at 7 under.
Bader had just completed No. 1 when lightning caused a 45-minute delay. When play resumed, she birdied each of the short par 5s to help offset a bogey at the par-4 fourth hole, her first bogey of the tournament.
Birdies at Nos. 6 and 7, the second on a 7-foot putt from above the hole that broke right to left, gave Bader sole possession of the lead. A bogey on the next hole when she was unable to get up and down after her second shot landed in a bad place next to a bunker dropped her back. She then rallied with a 12-foot birdie putt at No. 9 after her drive clipped a tree and landed in the first cut of the right rough.
That gave Bader 15 birdies over the first two rounds and a spot atop the leaderboard entering the weekend.
'I got lucky,' said Bader, who was caught and passed by Sorenstam late on the first round. 'I feel very good about coming back and shooting that score. I have had a few first-round leads and haven't played well the second day.'
Playing in a threesome with Creamer, Young Kim completed her second straight bogey-free round as the narrow, tree-lined Corning Country Club course yielded birdie after birdie on another day of hazy sunshine with temperatures approaching 90 degrees.
Kim's total of 132 included one eagle, 10 birdies and 25 pars.
'I just played my game,' said Kim, whose strong iron play helped her get through the round with just 26 putts. 'This is day two. I'm proud of myself. I knew if I hit my best shots it would be good. Before, I don't like this course because (it's) too narrow and (has) too small greens. Now, I'm feeling good.'
Creamer could have been feeling a lot better if she had taken advantage of the two easiest holes on the course. Instead, she three-putted for par at No. 2, a 445-yard par 5, and also parred the 449-yard fifth hole, another par 5, after hitting a tree off the tee.
Toss in a three-putt for bogey from 18 feet off the front fringe at the par-3 15th, and it's a wonder she still managed a big smile.
'You have to birdie those holes because those are easy birdie holes,' said the 20-year-old star, who finished her round with a 9-foot birdie putt at No. 9. 'It was kind of an up-and-down day. It's just one of those days. I don't feel like I played my best at all, and I shot 68. I'll take that.'
The Kims, who entered the day tied with 11 other players at 4 under, each shot 32 on the back side. But Mi Hyun Kim bogeyed No. 1 to fall back to 7 under, while Young Kim reeled off three birdies in a four-hole span to take sole possession of the lead at 11 under.
Young Kim, who started on the back nine, rolled in a 3-foot birdie putt on her final hole to finish one stroke off her personal best and move into contention for her first victory on the LPGA Tour.
'Before the 15th hole, I didn't think of my score,' said Kim, who sank a 21-foot birdie putt on the hole to reach 7 under. 'Then after I think, `Wow! I had a good score today.''
Sorenstam didn't. That bogey-free 64 Thursday became a distant memory after four bogeys on Friday. Still, she remained heartened by her position on the leaderboard.
'I'm happy the way I finished,' Sorenstam said. 'If I'm in the lead or not, or if I'm close to it, I'm happy there, too. I was just very proud of myself, that I was up there.'
Lightning halted play a second time just before 7 p.m. with 15 players still on the course.