The 200,000-member Amalgamated Transit Union, which supported Sen. Bernie Sanders (I-VT) in the 2016 Democratic Party primary, officially endorsed former Vice President Joe Biden Saturday over “electability.”

Politico reported that the union endorsed Biden after polling members, who emphasized “electability”:

The issue of Biden’s electability was the driving force behind the decision and a key concern of the union’s membership, which was randomly surveyed by phone in an “extensive poll” conducted by a professional pollster ATU hired, Costa said. “The numbers came back very strong for Joe,” Costa said, declining to discuss details of the “internal” survey. “Not only did people support him, but we asked who would be best to beat Trump, and he was overwhelmingly seen as the best to do it.”

Biden and Sanders are the two frontrunners in national polls heading into the Iowa caucuses on Monday.

Sen. Elizabeth Warren (D-MA) and former South Bend, Indiana, Mayor Pete Buttigieg are also in the top tier.

Sanders has led in recent polls in Iowa and New Hampshire, traditionally the two most important early primary states. He is statistically tied with Biden in the most recent Nevada poll, raising the prospect of a 1-2-3 sweep before the fourth contest, in South Carolina, where Biden has a healthy lead, thanks to African-American support.

The race has been stifled somewhat by the impeachment trial of President Donald Trump, which has kept Sanders and the other Senators in Washington, but has also mentioned Biden in a negative light.

Joel B. Pollak is Senior Editor-at-Large at Breitbart News. He earned an A.B. in Social Studies and Environmental Science and Public Policy from Harvard College, and a J.D. from Harvard Law School. He is a winner of the 2018 Robert Novak Journalism Alumni Fellowship. He is also the co-author of How Trump Won: The Inside Story of a Revolution, which is available from Regnery. Follow him on Twitter at @joelpollak.