Broadhurst, who also shared the first-round lead Thursday, had a 4-under 68 in what he said was his best driving day in months.
Fisher, a Wentworth member, overcame a mid-round collapse that cost him four strokes to birdie five of the last seven holes for a 70. He had a 12-foot eagle putt for the outright lead at the last but had to settle for birdie, tying Broadhurst at 10-under 206.
Richard Sterne had the day's low round of 66 to share third place with Marcus Fraser, who shot 70. They trail the leaders by a stroke.
Justin Rose, who shared the lead after the first two rounds, dropped three strokes on the front nine, then rallied to shoot 73 and stand alone in fifth place.
Broadhurst missed the cut in last week's Irish Open while he tried to correct a swing problem with his driver. He gave up on the new approach and went back to the old method.
'I drove it really solid today -- probably as good as I've ever driven it,' he said.
Fisher's best previous finish was fifth in this year's Dubai Desert Classic, where he played the last round with Tiger Woods and had a chance to win until the closing holes.
He chipped in for eagle at the fifth to take the lead, but two bogeys and a double over a three-hold stretch dropped him back.
'To win would absolutely be a dream come true. I probably won't be able to put it into words if it does happen,' said Fisher, who has played at Wentworth since he was a boy.
Rose, out of action with a back injury since finishing fifth at the Masters, had a poor day on the greens but is still within reach.
'I just couldn't read the greens,' he said. 'Let's hope that was my flat day.'
Seven of the world's top 15 players are in the field, led by Paul Casey in 10th place after a second-round 72.
Padraig Harrington, who won the Irish Open last week, shot 75 and shares 12th place, seven strokes off the lead.
Luke Donald shares 20th after a 71. Henrik Stenson and Vijay Singh were another shot back and Ernie Els, who redesigned the course, shot a 72 that included two eagles, four birdies, a triple bogey, a double bogey and three bogeys.
'It was wacky,' he said. 'Ridiculous.'