One of the nation’s largest unions accused President Obama of betraying workers and the labor movement by blocking the Keystone Pipeline and is backing up its rhetoric with campaign donations to Republicans.

The Laborers’ International Union of North America said that Obama’s bow to environmentalists meant that he was more concerned with "elitists" and "his legacy" than with helping workers provide for their families.

"President Obama today demonstrated that he cares more about kowtowing to green-collar elitists than he does about creating desperately needed, family-supporting, blue-collar jobs,"said Terry O’Sullivan, the union’s president, in a release following Obama’s Friday announcement.

Obama joined Vice President Joe Biden and Secretary of State John Kerry at the White House to announce that the administration would not approve the long-awaited TransCanada pipeline. He said that the pipeline and fossil fuel development and transportation "would not serve the national interest of the United States," while claiming that the State Department was ultimately responsible for the decision. He also downplayed the economic benefits of the multi-billion-dollar project.

"For years, the Keystone Pipeline has occupied what I, frankly, consider an overinflated role in our political discourse. It became a symbol too often used as a campaign cudgel by both parties rather than a serious policy matter," Obama said. "The pipeline would not make a meaningful long-term contribution to our economy."

O’Sullivan said that the White House’s approach to the approval process was one of "cowardly delay." He disputed the contention that Keystone was environmentally harmful, citing a 2014 State Department report that found not approving the pipeline would increase emissions by up to 42 percent.

"Facts apparently mean as little to the president as the construction jobs he repeatedly derided as insignificant because they are ‘temporary.’ Ironically, the very temporary nature of the president’s own job seems to be fueling a legacy of doing permanent harm to middle- and working class families," he said.

LIUNA represents about 500,000 workers in the construction industry, one of the sectors hardest hit by the 2008 economic collapse. Keystone, which was expected to create 42,000 construction jobs, has been awaiting approval for about seven years. O’Sullivan said that Obama’s attempt to minimize job gains demonstrated his "utter disdain" for blue-collar workers.

"The President’s decision to kill the Keystone XL Pipeline is just one more indication of an utter disdain and disregard for salt-of-the-earth, middle-class working Americans," O’Sullivan said. "The politics he has played with their lives and livelihoods is far dirtier than oil carried by any pipeline in the world, and the cynical manipulation of the approval process has made a mockery of regulatory institutions and government itself."

The union has contributed far more to Democrats than to the Republicans over the past 25 years, but that has changed so far in 2015, according to the Center for Responsive Politics.

LIUNA spent nearly $5 million on the 2012 elections to help Obama’s reelection. The union gave $750,000 to Obama reelection super PAC, Priorities USA. It contributed $1.1 million to House Democratic candidates, compared to less than $200,000 to GOP candidates. It gave nearly $100,000 on Senate races with all of that money going to Democrats.

The union was just as dedicated to helping elect Democrats in 2014, even as billionaire and green energy investor Tom Steyer pushed the party to the left on environmental issues. Its PAC sent $760,000 to liberal super PACs Senate Majority PAC and House Majority PAC, while contributing $1.5 million to Democratic campaigns and about $300,000 to Republicans.

Environmental issues have played a large role in the Democratic presidential primary with every single Democrat saying they would oppose the Keystone Pipeline. Hillary Clinton, who endorsed the pipeline as Obama’s secretary of state, flip-flopped on the issue in September.

"I think it is imperative that we look at the Keystone pipeline as what I believe it is—a distraction from important work we have to do on climate change," Clinton said at an Iowa campaign event.

The union may be undergoing a flip-flop of its own. It has donated more than $150,000 to House Republicans thus far in 2015—three times more than the $50,000 it has given Democratic candidates. Senate Democrats have received $17,000 compared to $7,500 for Republicans, but nearly all of those contributions have gone to pro-Keystone lawmakers, according to the Center for Responsive Politics.

The union gave $5,000 each to Florida Senate hopeful Rep. Patrick Murphy, one of a handful of House Democrats to vote for the pipeline, and Colorado Sen. Michael Bennet. Bennet criticized Clinton for refusing to take a stand on the issue in August. It also gave $4,500 to Sens. Jon Tester (D., MT) and Joe Manchin (D., WV), both of whom support the pipeline.

Russ Feingold, who lost his Wisconsin Senate seat in 2010, is the only Democratic candidate for the Senate to receive LIUNA cash and oppose Keystone.

The union’s super PAC, LIUNA Building America, has only made one donation in 2015: a $200,000 contribution to the pro-union Republican super PAC Defending Main Street. In 2014, the union PAC gave Defending Main Street just $50,000, while giving Democratic super PACs $465,000.

Keystone will play a role in shaping Obama’s legacy among workers, according to O’Sullivan.

"We are dismayed and disgusted that the President has once again thrown the members of LIUNA, and other hard-working, blue-collar workers under the bus of his vaunted ‘legacy,’ while doing little or nothing to make a real difference in global climate change. His actions are shameful," he said.