WASHINGTON, DC – NOVEMBER 18: U.S. Sen. Mary Landrieu (D-LA) speaks after the Senate voted on the Keystone XL Pipeline Bill at the U.S. Capitol on November 18, 2014 in Washington, DC. The vote failed to pass by a margin of 59-41. (Photo by Win McNamee/Getty Images).

After the House of Representatives overwhelmingly passed a measure authorizing the construction of the Keystone XL pipeline, Democrats successfully rallied to block the bill from passing a Senate vote yesterday.

The Post reports that the controversial bill, which calls for a 1,700-mile extension of the current Keystone pipeline system from Canada to the Gulf Coast, failed to overcome the Democrats’ filibuster, falling just one vote short of the 60 votes needed to pass. The proposal for an extension of the pipeline has been a contentious environmental issue, with environmental advocacy groups saying that the pipeline extension, which would cost $7.6 billion and carry more than 800,000 barrels of tar sand oil across the country per day, would leave a massive carbon footprint.

The issue has been a particularly difficult one for President Barack Obama, who has been torn between siding with environmentalists, or with moderate Democrats, like Sen. Mary Landrieu (D-La.), who supported the bill to help win votes from swing voters. From the Post:

In rejecting the bill, the Senate has granted Obama a temporary reprieve from a difficult decision: whether to side with the environmentalists who have been his staunch allies or with many moderate Democrats who hope to use the issue to win over swing voters.