Arsenal's title dream suffered another blow on Wednesday as Spurs recovered from two goals down to rescue a 3-3 draw, while Chelsea went above the Gunners into second place after beating Birmingham 3-1.
Arsene Wenger's side were on course to move within four points of leaders Manchester United after taking a 3-1 lead at White Hart Lane.
But Wenger's often-criticised defence failed him again and Rafael Van der Vaart scored a second half penalty equaliser to condemn Arsenal to a fifth draw in six Premier League games.
As a result they lost second place to a resurgent Chelsea, who are now six points behind United with a crucial trip to Old Trafford looming in May.
Wenger, whose side were held 1-1 by Liverpool on Sunday, said: "Of course we have regrets because we were 3-1 up but the second was an outstanding goal and then we conceded a penalty.
"We had a fantastic attitude in the first half but dropped in the second half because it is a massive disadvantage playing two games of such stature in a matter of days.
"We will fight like mad for the next game. Of course we can still win the title."
Chelsea manager Carlo Ancelotti added: "With a six-point lead Manchester United is still too far but we have to believe.
"I never said the title race was over. After this we have to play five games. We have to win them all and see what happens."
After the pain of Sunday's draw against Liverpool, Arsenal needed an early boost and they got it when Theo Walcott lit the fuse on an explosive first half by sprinting onto Cesc Fabregas's pass and slotting past Heurelho Gomes.
Arsenal's lead was short-lived as Dutch international Van der Vaart beat the offside trap to score with a ferocious finish two minutes later.
But the Gunners were back in front in the 12th minute when France midfielder Samir Nasri hit a low shot from the edge of the area that took a slight deflection off Spurs defender Michael Dawson before beating Gomes.
Wenger's team increased their lead through Robin van Persie in the 40th minute.
Walcott hooked a cross back from the touchline and, after Gomes had saved Van Persie's initial effort, the Dutch forward was able to fire in from close-range.
Even then Spurs refused to surrender. Harry Redknapp's side had come from two goals behind to beat Arsenal 3-2 earlier this season and recovered from 4-2 down to earn a 4-4 draw against the Gunners in 2008.
Tom Huddlestone gave Spurs a lifeline four minutes later with a powerful long-range effort that fizzed through Van der Vaart's legs and beyond goalkeeper Wojciech Szczesny.
And the hosts completed a superb comeback in the 70th minute when Szczesny fouled Aaron Lennon and Van der Vaart stroked in the resulting penalty.
"That was one of the great games in my opinion. It was a little classic," Redknapp said.
"We came back from an almost impossible position. There is a fantastic spirit at this club and we never give in."
At Stamford Bridge, Chelsea produced a second dominant display in five days to keep a foothold in the title race.
After beating West Bromwich Albion 3-1 on Saturday, Ancelotti's side avenged their 1-0 loss against Birmingham earlier this season to revive belief they can retain the title.
Chelsea took the lead in the third minute when Paulo Ferreira's cross was flicked on by Didier Drogba and French winger Florent Malouda pounced to poke home from close-range.
Ancelotti again left British record signing Fernando Torres and France striker Nicolas Anelka on the bench as he opted for Drogba as his lone forward supported by Malouda and Salomon Kalou.
Ivory Coast forward Kalou justified his inclusion as he scored with a sensational strike that saw him beat two Birmingham defenders before drilling an unstoppable shot past Ben Foster in the 26th minute.
Malouda put the game out of Birmingham's reach in the 62nd minute when he headed in a cross from debutant Ryan Bertrand.
Sebastian Larsson got one back for Birmingham with a 76th minute after David Luiz fouled Matt Derbyshire, but it was little consolation for Alex McLeish's team, who remain five points above the relegation zone.