Steve Seddon’s 93rd-minute strike salvaged a 2-2 draw for the Dons at Kenilworth Road this evening.
First-half efforts from Elliott Lee and the division’s leading scorer James Collins had looked to have put Mick Hardford’s table-toppers within a win of the Championship with two games to play.
But after Wimbledon’s late leveller, the Hatters now require four points from their final two matches to guarantee promotion.
Leaders Luton have a three-point cushion over Barnsley, in second, with two games to go.
And it leaves Harford’s troops just five points clear of third-placed Pompey, with Kenny Jackett’s men having played a match less.
The Hatters’ remaining games are at Burton on Saturday before they host Oxford on the final day.
And the late drama has given Pompey, Barnsley and Sunderland of catching Luton in the race to reach the Championship.
Meanwhile, Doncaster’s play-off aspirations took a hit following a 2-1 defeat to Accrignton at the Keepmoat Stadium.
Donny, who sit in sixth, could not turn around a two-goal half-time deficit after strikes from Sean McConville and Paul Smyth put Accy in control at the break.
Danny Andrew struck in stoppage-time but it was too little, too late for Grant McCann’s troops.
Despite the defeat, Doncaster still occupy the final play-off place with two games to play.
Although they are just three points ahead of seventh-placed Peterborough, having played a game more.
Coventry, in eighth, can also sneak into the play-offs. But face a tall order to turn around a five-point deficit in the final two matches.