Goals from Fabio Borini, Mark Gower and Tamas Priskin threw the automatic promotion race wide open as Swansea beat second-place Norwich.
Italian Borini set the ball rolling with a superbly-struck 30-yard free-kick into the top corner.
Gower drilled home from the edge of the box to double the lead, before Priskin sealed the win in injury-time.
Norwich had chances through Grant Holt and Simeon Jackson but Swans keeper Dorus de Vries was in fine form.
Swansea stay fourth, level on 69 points and goal difference with Cardiff City but the two Welsh sides are now just a point off Norwich, who saw their nine-match unbeaten run come to an end.
The Swans knew only a win would do if they were to realistically keep their automatic promotion hopes alive.
Having already taken promotion rivals Leeds and Nottingham Forest to task on home soil, Norwich were their next targets, but the Canaries have been scoring goals for fun.
It was therefore no surprise that Norwich took the game to Swansea and goalkeeper De Vries had to make a fine double-save to keep them out after just four minutes.
The first came when Dani Pacheco was allowed to skip into the box and fire at goal and De Vries' parry fell into the path of Holt, but the alert Dutchman denied him too.
Then within a minute, Norwich were made to pay when Zak Whitbread hacked down Borini 30 yards out and the Italian Under-21 international picked himself up to superbly send the resulting free-kick into the top left-hand corner for his third goal in as many games.
Top-scorer Holt posed the visitors' biggest threat and he was involved in most of their moves as they tried to level.
The Canaries captain was on the end of a neat build-up around the Swansea box before dragging his shot across the face of goal.
And midway through the first half, Andrew Crofts floated in a delightful ball from the right-hand byline which Holt met at the far post only to head into the side-netting.
Once again, Paul Lambert's side were left to rue missed opportunities as the Swans went on to double their lead on 29 minutes.
Right-back Angel Rangel raced into the box before launching a shot at John Ruddy, who could only parry.
Norwich failed to clear their lines leaving Gower to drill a sweetly struck half-volley into the bottom corner from just outside the box.
It could have been 3-0 had it not been for the quick reaction by Ruddy to close down Borini after being put through on goal by Nathan Dyer.
And then in first-half stoppage time, Whitbread came to Norwich's rescue with a superbly-timed challenge in the box to clear the danger from Borini.
Norwich threw on Jackson at the restart for Andrew Surman and almost got themselves back into the game within a minute.
Holt won a free-kick and was on the end of Pacheco's delivery but somehow powered his six-yard header wide.
And then just before the hour, Crofts collected the ball on the edge of the box and drilled inches wide of the upright, before later hitting a tame shot straight at De Vries.
That was Crofts' last action as he was brought off for Korey Smith while Sam Vokes replaced Pacheco and Lambert pushed three up front.
De Vries repeated his first-half double save on 71 minutes when he pushed away two fine strikes from Smith.
Swans substitute Priskin wasted one chance to put the game to bed by firing straight at Ruddy.
But the on-loan Ipswich striker made amends by pouncing on a weak Whitbread backpass to beat Ruddy to the loose ball, leaving him with the simplest of tasks to roll the ball into an empty net.