The endorsement was the result of a months-long process that included scientific polling of Teamster members, surveys of local union and joint council leaders and deliberations by the union's democratically elected General Executive Board.
"In these years that I've been in office, I've seen and appreciated how you support the American economy and social justice, a tradition that goes back more than a 100 years," President Obama said by phone to Teamsters at the Las Vegas conference. "America would look a lot different without the Teamsters."
In a statement, Hoffa said the union wants to keep the likely Republican presidential candidate, Mitt Romney, out of the White House, calling him a "vulture capitalist."
"Mitt Romney would be the fox guarding the henhouse," he said.
As recently as late last year, Politico notes, several labor leaders, disappointed the president hadn't focused on their agenda as much as they'd hoped, warned that they might sit out the 2012 election cycle in protest.
The Teamsters union also endorsed Obama in 2008 over Democratic primary rival Hillary Clinton.
In recent years, the Teamsters have been working to organize port drivers, but in most cases, the drivers are independent contractors that can't be unionized. Because of this, the Teamsters have been pushing for laws that target "misclassification" of employees as contractors.
They've also been recently involved in pushing for an electronic onboard recorder mandate.
Founded in 1903, the Teamsters Union represents 1.4 million men and women throughout the U.S., Canada and Puerto Rico.
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