CHICAGO – The Chicago Teachers Union’s interim president, Jesse Sharkey, believes Rahm Emanuel’s days are numbered as Chicago mayor.

Sharkey cast his prediction for ChicagoMag.com after Cook County commissioner Jesus “Chuy” Garcia forced an April run-off election by holding incumbent Emanuel to less than 50 percent of the vote in Tuesday’s election.

Sharkey took over the CTU after former president Karen Lewis, who was mulling a run at mayor, was diagnosed with brain cancer. Garcia entered the mayor’s race late, when Lewis bowed out, and it was the CTU’s efforts to push Garcia that made the difference this week, Sharkey told Chicago Mag.

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“We brought a lot of very committed people to his contest, especially in parts of the south and west sides,” Sharkey said. “We had 100-percent committed volunteers working outdoors in brutally cold weather. We had phone banks going around the clock. The CTU played an important role in getting Chuy to run.”

Sharkey predicts Garcia will build momentum heading into an April 7 run-off with Emanuel, and it will be education issues that will give Garcia the edge.

“Schools were the marquee issue of this campaign and Rahm suffered losses because of his high-handedness in relation to school issues,” Sharkey said.

“The takeaway is the mayor is going to lose. The point is that Chuy has momentum. Rahm can’t run away from the fact that he closed 50 schools, that he opposes an elected school board, that his donors list is full of rich people, many who live out of state or in the suburbs.

“Rahm gets six-figure checks and gives out political favors more than half the time,” Sharkey continued. “Those are the issues that stick to the mayor. So it’s a rebuke for his political program but I think it’s also a wake-up call for elected officials who can now see that even on a brutally cold day people will turn out to push this city in a different direction.”

Reuters reports Emanuel managed to secure only 45.4 percent of the vote in Tuesday’s mayoral contest, less than the roughly 50 percent predicted in polling. Garcia secured about 33.9 percent of the vote, about 13 percentage points higher than polling indicated before Election Day.

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The election results were somewhat surprising as Emanuel’s campaign war chest topped $6 million at the end of 2014, despite spending $4.7 million in the fourth quarter, according to Reuters.

Emanuel vowed to press on despite the disappointing election results.

“We will get back out there talking to our friends and families and neighbors as they make a critical choice about who has the strength, who has the leadership, who has the ideas to move this great city forward,” Emanuel said.

But it’s not only Sharkey talking about Garcia gaining momentum, as some who spoke with Reuters seem to be shifting their support.

Former Emanuel supporter Suzy Broz, 26, told Reuters “a lot of people are upset with the one percent mayor and people feel that there’s a great chance for change.”