Thousands of activists opposed to a plan to build a 1,700-mile oil pipeline that cuts through the heart of the United States descended on the White House on Sunday to ratchet up the pressure on President Obama to scrap the project.

The protest of TransCanada’s Keystone XL pipeline came exactly one year before the 2012 election and was designed to send a message to Obama that failure to act will lead to a drop-off in enthusiasm from the environmentalists who backed him in 2008.

The project pits environmentalists against Republicans and many top labor groups — with both sides suggesting that the president will pay politically if he doesn’t side with them. Backers of the project say the pipeline will create thousands of jobs and help reduce U.S. dependence on Middle Eastern oil.