Pettersen, the Norwegian star ranked sixth in the world, shot 4-under-par 68 at Blackwolf Run on Friday and moved to 5-under for the tournament.
But Wie was even better on the day, carding 66 to move within a shot of the lead and put herself in position to break out of a season-long slump.
Wie is tied with Cristie Kerr, the 2007 Open winner, one stroke off the lead.
Pettersen was playing in the group directly behind Wie, giving her a good view of Wie’s round.
“She was fist-pumping, every putt she looked at,” Pettersen said.
Wie said she doesn’t spend much time thinking about the attention she received as a high-profile child prodigy in the early 2000s, or whether some fans had written her off since then.
“I don’t know if anyone gave up on me or not,” Wie said. “I’m sure some did and some didn’t. But I never gave up on myself, and today was a good reminder to myself that I can do (it) and I still have it.”
Kerr, who was tied for the first-round lead at 69 with Lizette Salas and Brittany Lincicome, had 71.
“I always draw on that experience, of course, but it’s hard to predict what’s an advantage and what’s not an advantage,” Kerr said of her previous Open win. “You just don’t know.”
Sandra Gal, Inbee Park and Vicky Hurst shot 70 to reach 3under.
Salas, a 22-year-old recent Southern California graduate, had 73 to drop to 2 under. Mika Miyazato also was 2-under after 71.
Lincicome had a miserable day, shooting 80 to fall to 5-over.
Seventeen-year-old Lexi Thompson shot 73 to top the group at 1-under.
Top-ranked Yani Tseng was 2-over after 72.
Second-ranked Stacy Lewis recovered from a first-round 77 to shoot 69 on Friday, putting her 2 over.
Defending champion So Yeon Ryu shot 71 and was 1-over.
Se Ri Pak, the Open winner at Blackwolf Run in 1998, also was 1-over after 73.