Nick Chadwick has scored four goals for the Hatters this season
Cambridge twice battled back from behind to condemn 10-man Stockport to a seventh consecutive away draw.
The Hatters took an early lead when striker Nick Chadwick headed home from John Miles' free-kick.
Luke Berry equalised for the hosts with a fine finish from the edge of the area before substitute Danny Whitehead nodded the visitors ahead once more.
Jordan Patrick levelled from a tight angle after Carl Piergianni saw red for a second bookable offence.
VIEWS FROM THE DRESSING ROOM
Cambridge United manager Jez George told BBC Radio Cambridgeshire:
"I don't think we started the game very well, obviously the early goal doesn't help.
"That's two games running we've done that, so it's disappointing, as were the nature of the goals.
"We did improve and we started passing the ball and when we did that we looked dangerous and created some decent stuff."
Cambridge Utd 01 Naisbitt 02 Roberts 03 Jennings 04 Coulson 12 McAuley 10 Carew (Patrick - 66' ) 16 Jarvis 18 Berry 09 Gash (Dunk - 76' ) 19 Marriott (Charles - 67' ) 21 Winn Substitutes 25 Blaine Hudson 27 Thorpe 11 Dunk 20 Patrick 07 Charles Stockport 01 Glennon 05 O'Donnell 21 Bounab Booked 22 Piergianni Dismissed after an earlier booking 24 Edwards 08 Nolan 14 Sheridan 10 Miles (McCann - 82' ) 19 Chadwick (Blackburn - 67' ) 20 Elliott Booked 23 Paton (Whitehead - 46' ) Substitutes 12 Ormson 06 German 25 Blackburn 16 McCann 15 Whitehead