The Union (11-7-9, 42 points) moved from the seventh and final playoff spot, to a tie with Orlando City for third in the Eastern Conference.
Columbus (9-12-7, 34), the reigning MLS Cup champion, is in peril of missing the playoffs. The Crew are tied for ninth with the New York Red Bulls in the East, six points behind Montreal with six matches left.
Philadelphia is 3-0-1 in the past four games.
Goals by Jack Elliott in the 25th minute and Alex Bedoya in the 46th gave the Union the lead before Kai Wagner was ejected for a second yellow card in the 64th minute, throwing a lifeline to the Crew.
Blake, who made three saves for his career-best-tying 10th shutout this season, had an outstanding stop on a curling strike by Darlington Nagbe in the 80th minute.
It was tough game for Bush.
Elliott's goal, the second of the season for the central defender, was either very fortunate or well placed. He lined up from 30 yards and the shot went around the wall to the near post where it bounced twice before eluding Bush.
"I can't say it was a great free kick," Union coach Jim Curtin said at halftime on the television broadcast.
The Crew dug a deeper hole only 30 seconds into the second half when Bedoya scored his second goal of the season on a give-and-go with Kacper Przybylko.