One of the labor movement’s most ardent critics of Barack Obama declared Friday that he and his organization were squarely behind the president’s reelection.

President Obama speaks at the University of Miami Field House in Coral Gables, Fla., Thursday, Feb. 23, 2012. (Susan Walsh/Associated Press)

Four years ago, Tom Buffenbarger, head of the International Association of Machinists, and a staunch Hillary Clinton backer, became a YouTube sensation assailing then-Sen. Obama for abandoning workers and trying to ride his lofty oratory to the White House.

“Hope. Change. Yes we can. Give me a break,” Buffenbarger boomed during one 2008 appearance in which he ripped Obama as a “two-faced” academic appealing more to rich college kids than assembly-line workers. “I’ve got news for all the latte-drinking, Prius-driving, Birkenstock-wearing, trust-fund babies crowding in to hear him speak. This guy won’t last around against the Republican attack machine. He’s a poet, not a fighter.”

But now, as Obama courts labor unions as part of his reelection effort, the machinists are singing a different tune.

“Jobs are the central issue of this campaign, and only President Obama has a plan that would put millions of Americans and thousands of Machinists back to work,” Buffenbarger said in a statement released from the union. “We’re convinced the job growth we’re now seeing, particularly in the critical manufacturing sector, is a direct result of President Obama’s policies and leadership and we want that growth to continue.”

The statement continued: “Our policy differences with the White House in the past have dealt with the pace and speed of this recovery. IAM members recognize that GOP presidential candidates and Republican Congressional leaders have placed obstacle after obstacle in President Obama’s path. We intend to work overtime to remove those obstacles.”

The announcement underscores the new political realities inside the labor movement — which has expressed disappointment with Obama over the years, in part because many labor leaders feel he did not push strongly enough for new legislation to make it easier to form a union. Relations between Obama’s team and many labor leaders, particularly Buffenbarger, have been cool at best.

Still, in recent months, the White House has worked to soothe relations. Unions have been engaged in combat with Republican governors and lawmakers, and the movement is now preparing to unleash millions of dollars to help the Obama reelection effort. The American Federation of State, County and Municipal Employees, for instance, has already signaled it will spend as much as $120 million this year.

The machinists’ news release issued Friday noted that the endorsement “sets the stage for significant volunteer activity” on Obama’s behalf by the group’s 700,000 members.