Benny Feilhaber was the hero for Sporting KC, scoring a 93rd-minute goal as the visitors emerged triumphant in a dramatic fixture that saw both teams finish with 10 men at Columbus Crew Stadium.
The match seemed destined for a draw after a 69th-minute own goal from Sporting KC midfielder Igor Juliao - on loan from Brazil's Fluminense - cancelled out Charles Sapong's first-half opener.
But with only seconds remaining, Brazil-born Feilhaber fired a shot off the crossbar and into the net in the third minute of injury time - condemning the Crew to back-to-back losses.
In the midst of an action-packed second half, Sporting KC defender Aurelien Collin was shown a straight card for an aerial challenge on Adam Bedell in the 55th minute, while Wil Trapp was dismissed for a second bookable offence after 89 minutes.
High-flying Sporting KC have collected 32 points from 19 games and are one point clear in the East, though they have played an extra game than rivals DC United.
Consecutive defeats have left Columbus (20 points) in seventh position in the Eastern Conference, three points adrift of the fifth-placed New York Red Bulls and the play-off spots.
News of the Crew's extended winless streak, which now stands at seven games, would have pleased the Red Bulls, who were beaten 3-1 by the Philadelphia Union.
Having gone five games unbeaten, the Red Bulls travelled to PPL Park full of confidence, but they came crashing back down to earth following goals form Union trio Conor Casey, Fred and Sebastien Le Toux.
Former United States international Casey opened the scoring in the ninth minute and the home side doubled their advantage six minutes after the half-time interval courtesy of ex A-League striker Fred.
New York found themselves back in the contest on the hour-mark when striker Bradley Wright-Phillips - the competition's leading scorer - took his tally to 15 goals for the season after he placed the ball beyond Union goalkeeper Zac MacMath.
However, the Union put the result beyond doubt in the 69th minute following Le Toux's successful penalty after Maurice Edu was fouled by Eric Alexander inside the area.
Philadelphia are only one point behind the Red Bulls, but New York have a game in hand.
In other results on Wednesday, Toronto missed the chance to close the gap on Sporting KC after they were held to a 1-1 draw by the Vancouver Whitecaps in their all-Canadian affair.
Vancouver's Darren Mattocks broke the deadlock five minutes into the second half, only for England international Jermain Defoe to level proceedings from the penalty spot 14 minutes later - his eighth goal in nine league games.
Toronto are third in the East with 25 points, though they do have three games in hand.
Meanwhile, two goals apiece from Robbie Keane and Gyasi Zardes inspired the 10-man Los Angeles Galaxy to a 5-1 rout of the New England Revolution, who also ended the match with 10 men at Stubhub Center.
Stefan Ishizaki was the other goal scorer for the Galaxy in the second half, while New England's Lee Nguyen got himself on the scoresheet courtesy of a 38th-minute penalty.
Los Angeles defender Dan Gargan and New England's Anthony Soares were both dismissed before the 40-minute mark but the Galaxy came out on top as they rose to third in the West.
