In a swipe at the White House, the Service Employees International Union (SEIU), one of the largest labor organizations in the country, has endorsed Jesus “Chuy” Garcia over sitting Chicago Mayor Rahm Emanuel. Emanuel is President Barack Obama’s former Chief of Staff and is considered a major player in Democratic politics.

Tom Balanoff, President of SEIU Local 1, told the Chicago Sun-Times, “We think there is a clear contrast between Chuy Garcia and Rahm Emanuel.”

Adding, “Mayor Emanuel doesn’t understand that what made Chicago great was working people. We think he has totally turned his back on that.”

The mayoral race is heading to an April 7 run-off after no candidate reached 50 percent of the vote in last month’s election, the first time in the city’s history that a sitting mayor has been forced into one.

The SEIU endorsement comes with a lot of union money, as much as $2 million. While it’s unclear exactly how much the SEIU will commit to Garcia, he managed to come in second in the general election despite having been outspent 12 to 1. Garcia only raised $1.2 million for the general run, while Emanuel had amassed a $15 million war chest.

Democrats have long been the favorite party of unions and benefited greatly from their political donations. But that relationship appears to have suffered under President Obama.

The top priority of unions is “Card Check” legislation, removing the secret ballot from the unionization process. They want to make it easier to pressure employees to unionize because their ranks have dwindled over the past few decades. Democrats, including the president, promised it would be a top priority during the 2008 campaign, but failed to move legislation when they had super-majorities in Congress during Obama’s first 2 years.

That wound, coupled with budget cuts, appears to have been the straw that broke the camel’s back.

Balanoff told NBC in Chicago “he was upset with the cutbacks at O’Hare International Airport and with the school closings.”

Emanuel still enjoys the support of many other unions, but the SEIU endorsement of his opponent is another major blow in what was already a surprising election cycle.