With a rumoured £5million bonus put up by Seasiders president Valeri Belokon if his team reaches the Premier League, everything was staked.
Blackpool needed Swansea to be held at Doncaster and, with that match finishing two minutes earlier, the draw at Bloomfield Road proved almost incidental as the crowd invaded the pitch.
Ormerod's goal came on 52 minutes after the striker was fouled by Louis Carey just outside the penalty area.
Scotland international Charlie Adam delivered the perfect free-kick which Ormerod flung himself at full length to head into the top corner.
City had gone ahead silencing the vocal home support on 17 minutes. The goal came direct from a goal-kick by Dean Gerken which eluded the Blackpool defence.
Nicky Maynard latched onto it and volleyed beautifully over Matt Gilks, who was perhaps too far off his line.
Blackpool had far more creativity in midfield thanks to the promptings of Adam and the tireless David Vaughan, but it was at the back where the Seasiders based their victory with a powerful display from centre half Ian Evatt and Seamus Coleman.
It took Blackpool time to recover from Maynard's stunner and after the game Blackpool manager Ian Holloway went onto the pitch and said: "Never in my life have I seen such a performance from a group of lads written off by everyone at the start of the season - we can go all the way."
City refused to lay down and, if Gilks had been at fault for their goal, the Blackpool keeper made amends with a superb save from Jamal Campbell-Ryce in the final stages.
Blackpool swept back into attack and substitute striker Ben Burgess could so easily have wrapped up a victory but his header clipped the top of the bar.