Leicester will be crowned Barclays Premier League champions with a win next weekend after Craig Dawson's header held Tottenham to a 1-1 draw against West Brom.
Spurs' surprise slip-up at White Hart Lane means Leicester are seven points clear with three games remaining and the Foxes' fairytale will be complete if they beat Manchester United at Old Trafford on Sunday.
Mauricio Pochettino's men looked on course for another comfortable victory when Dawson bundled in a first-half own-goal but the defender redeemed himself, heading home with 18 minutes left to leave Tottenham's title hopes hanging by a thread.
A disappointing night for Spurs could become worse too as Eric Dier was forced to leave the field following a clash of heads with Dawson in the second half, while Dele Alli may face a retrospective ban for appearing to punch West Brom's Claudio Yacob.
Alli began the night collecting his PFA Young Player of the Year award in front of the Tottenham supporters but the midfielder let his frustrations boil over early on with an unnecessary act of petulance.
Referee Mike Jones did not seem to see the incident but the 20-year-old could yet face a three-match suspension if found guilty of violent conduct, a punishment which would rule him out for the rest of the season.
Tottenham dominated the opening exchanges and within 12 minutes had twice hit the woodwork as Harry Kane bounced a one-two off Alli, but saw his finish tipped onto the post, before Christian Eriksen's whipped free-kick grazed the top of the crossbar.
Alli had undergone some heavy challenges early on and he took his frustration out on Yacob, turning and swinging his hand into the midfielder's stomach when referee Jones was looking the other way.
Surviving the early onslaught, West Brom dropped deep, happy to let the hosts dictate possession while Spurs fans vented their frustration as early as the 22nd minute when the Baggies took their time over a throw-in.
In fact, the visitors could have taken the lead when Craig Gardner blazed over from inside the area and moments later Spurs made them pay, as Jan Vertonghen and Dawson tussled to meet Eriksen's free-kick, with the latter bundling the ball under Boaz Myhill for an own-goal.
With the deadlock broken, Tottenham began to enjoy themselves, Mousa Dembele flicking his way nonchalantly through Darren Fletcher and the home supporters launching into an optimistic rendition of "Leicester City, we're coming for you".
All that seemed left was for the hosts to score a second and they nearly did so just before the hour mark when Erik Lamela skewed Eriksen's pullback onto the post and Kane was unable to turn in the rebound.
As the game drifted into the latter stages, however, West Brom began to turn the tide. Salomon Rondon heading Gardner's cross wide was a warning which went unheeded as in the 72nd minute Dawson climbed above both Dier and a flailing Hugo Lloris to head home an equaliser from a Gardner corner.
Dier took a blow to the head trying to defend the goal and had to be substituted, while Nacer Chadli was also introduced late on as the hosts desperately searched for a winner.
There were to be no late heroics, however, as Tottenham's title challenge finally hit the buffers, leaving Leicester on the brink of glory.
Tottenham Hotspur: Lloris, Walker, Alderweireld, Vertonghen, Rose, Dier (Mason 75), Dembele, Lamela (Son 85), Alli (Chadli 90), Eriksen, Kane.
Subs Not Used: Vorm, Trippier, Carroll, Davies.
Goals: Dawson 33 og.
West Brom: Myhill, Dawson, McAuley, Olsson, Evans, Yacob, Fletcher, Sessegnon (Sandro 90), Gardner,McClean, Rondon.
Subs Not Used: Chester, Anichebe, Lambert, Roberts, Leko, Palmer.
Goals: Dawson 73.
Ref: Robert Madley (West Yorkshire).