James Hanson's late winner heaped further pressure on Leeds head coach Dave Hockaday as Bradford claimed a 2-1 victory in a fiery West Yorkshire derby to progress to the third round of the Capital One cup.
Beaten finalists two seasons ago, the Bantams were again keen to impress in front of the television cameras as they recorded their first win over United for almost 28 years.
Hockaday, who was given a stay of execution by club president Massimo Cellino following Saturday's 4-1 defeat at Watford, looked a relieved man when Matt Smith headed them in front eight minutes from time.
But a stunning equaliser from Billy Knott soon lifted the home crowd and again, and they were simply delirious when Hanson prodded over the line with four minutes remaining.
Bradford claimed an early advantage when Leeds, who have already received three red cards this season, were reduced to 10 men after Luke Murphy was shown a second yellow card for a reckless challenge on James Meredith.
But after spurning a number of chances it looked as though it would not be their night when United, largely against the run of play, took the lead when David Norris picked out Smith with a pin-point cross to head home from close range.
However, they were ahead for just two minutes as United failed to clear Alan Sheehan's original corner, only for Billy Knott to fire in a stunning equaliser from 30 yards.
And the Bantams completed an historic win little over 60 seconds later when Gary Liddle's cross fell into the path of Hanson who had the easiest of finishes, condemning their bitter rivals to a fourth defeat in six outings, leaving Hockaday's position in further jeopardy.