Sanders campaign endorsed by MoveOn.org

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WASHINGTON (AP) -- Democratic presidential candidate Bernie Sanders on Tuesday received the endorsement of MoveOn.org, a grassroots organization that has been at the forefront of liberal causes.

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MoveOn says the Vermont senator was supported by 78.6 percent of its membership in an online vote of more than 340,000 members. Hillary Clinton received 14.6 percent and Martin O'Malley received 0.9 percent with the remaining members urging no endorsement.

"MoveOn members are feeling the Bern," said Ilya Sheyman, executive director of MoveOn.org Political Action. "We will mobilize aggressively to add our collective people power to the growing movement behind the Sanders campaign, starting with a focus on voter turnout in Iowa and New Hampshire

Click though pictures of Bernie Sanders and Hillary Clinton at the Democratic debate:

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Bernie Sanders and Hillary Clinton duking it out during Democratic debates
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Sanders campaign endorsed by MoveOn.org
Democratic presidential candidate, Sen. Bernie Sanders, I-Vt and Democratic presidential candidate, Hillary Clinton interrupt each other during the Univision, Washington Post Democratic presidential debate at Miami-Dade College, Wednesday, March 9, 2016, in Miami. (AP Photo/Wilfredo Lee)
Democratic presidential candidate, Hillary Clinton argues a point as Sen. Bernie Sanders, I-Vt., right, listens during a Democratic presidential primary debate at the University of Michigan-Flint, Sunday, March 6, 2016, in Flint, Mich. (AP Photo/Carlos Osorio)
Democratic presidential candidate, Hillary Clinton makes a point as Sen. Bernie Sanders, I-Vt, reatcs during a Democratic presidential primary debate at the University of Wisconsin-Milwaukee, Thursday, Feb. 11, 2016, in Milwaukee. (AP Photo/Morry Gash)
MILWAUKEE, WI - FEBRUARY 11: Democratic presidential candidate Senator Bernie Sanders (L) and Hillary Clinton participate in the PBS NewsHour Democratic presidential candidate debate at the University of Wisconsin-Milwaukee on February 11, 2016 in Milwaukee, Wisconsin.The debate is the final debate before the Nevada caucuses scheduled for February 20. (Photo by Win McNamee/Getty Images)
Democratic presidential candidate, Sen. Bernie Sanders, I-Vt., gestures towards Democratic presidential candidate, former Secretary of State Hillary Clinton during a democratic presidential primary debate at the Gaillard Center, Sunday, Jan. 17, 2016, in Charleston, S.C. (AP Photo/Mic Smith)
Democratic presidential candidate, Hillary Clinton, left, speaks at the NBC, YouTube Democratic presidential debate at the Gaillard Center, Sunday, Jan. 17, 2016, in Charleston, S.C. To the right is Democratic presidential candidate, Sen. Bernie Sanders, I-Vt. (AP Photo/Stephen B. Morton)
Democratic presidential candidate, Hillary Clinton and Democratic presidential candidate, Sen. Bernie Sanders, I-Vt. speak during a break at the NBC, YouTube Democratic presidential debate at the Gaillard Center, Sunday, Jan. 17, 2016, in Charleston, S.C. (AP Photo/Mic Smith)
DURHAM, NH - FEBRUARY 04: Democratic presidential candidates former Secretary of State Hillary Clinton and U.S. Sen. Bernie Sanders (I-VT) during their MSNBC Democratic Candidates Debate at the University of New Hampshire on February 4, 2016 in Durham, New Hampshire. This is the final debate for the Democratic candidates before the New Hampshire primaries. (Photo by Justin Sullivan/Getty Images)
Hillary Clinton, right, speaks to Bernie Sanders during a break at the Democratic presidential primary debate Saturday, Dec. 19, 2015, at Saint Anselm College in Manchester, N.H. (AP Photo/Jim Cole)
Bernie Sanders, left, offers an apology to Hillary Clinton during a Democratic presidential primary debate Saturday, Dec. 19, 2015, at Saint Anselm College in Manchester, N.H. (AP Photo/Jim Cole)
Bernie Sanders, left, speaks to Hillary Clinton after a Democratic presidential primary debate Saturday, Dec. 19, 2015, at Saint Anselm College in Manchester, N.H. (AP Photo/Jim Cole)
Bernie Sanders, left, makes a point as Hillary Rodham Clinton listens during a Democratic presidential primary debate, Saturday, Nov. 14, 2015, in Des Moines, Iowa. (AP Photo/Charlie Neibergall)
Hillary Rodham Clinton, right, walks by Bernie Sanders during a commercial break at a Democratic presidential primary debate, Saturday, Nov. 14, 2015, in Des Moines, Iowa. (AP Photo/Charlie Neibergall)
FILE - In this Nov. 14, 2015, file photo, Bernie Sanders makes a point during a Democratic presidential primary debate in Des Moines, Iowa. The Democratic presidential candidates are meeting for their third debate on Dec. 19, with tensions suddenly boiling between Hillary Clinton and her chief rival, Sanders. (AP Photo/Charlie Neibergall, File)
Democratic presidential candidates Hillary Rodham Clinton, left, Bernie Sanders and Martin O'Malley appear before a Democratic presidential primary debate, Saturday, Nov. 14, 2015, in Des Moines, Iowa. (AP Photo/Charlie Neibergall)
Hillary Rodham Clinton, right, and Sen. Bernie Sanders, of Vermont, speak during the CNN Democratic presidential debate Tuesday, Oct. 13, 2015, in Las Vegas. (AP Photo/John Locher)
Democratic presidential candidates from left, former Virginia Sen. Jim Webb, Sen. Bernie Sanders, of Vermont, Hillary Rodham Clinton, former Maryland Gov. Martin O'Malley, and former Rhode Island Gov. Lincoln Chafee take the stage before the CNN Democratic presidential debate Tuesday, Oct. 13, 2015, in Las Vegas. (AP Photo/John Locher)
LAS VEGAS, NV - OCTOBER 13: Democratic presidential candidates Sen. Bernie Sanders (I-VT) (L) and Hillary Clinton take part in a presidential debate sponsored by CNN and Facebook at Wynn Las Vegas on October 13, 2015 in Las Vegas, Nevada. Five Democratic presidential candidates are participating in the party's first presidential debate. (Photo by Joe Raedle/Getty Images)
Senator Bernie Sanders, an independent from Vermont, left, and Hillary Clinton, former U.S. secretary of state, participate in the first Democratic presidential debate at the Wynn Las Vegas resort and casino in Las Vegas, Nevada, U.S., on Tuesday, Oct. 13, 2015. While tonight's first Democratic presidential debate will probably lack the name-calling and sharp jabs of the Republican face-offs, there's still potential for strong disagreements between the party's leading contenders. Photographer: Josh Haner/Pool via Bloomberg
Sen. Bernie Sanders, of Vermont,, left, and Hillary Rodham Clinton laugh during the CNN Democratic presidential debate, Tuesday, Oct. 13, 2015, in Las Vegas. (AP Photo/John Locher)
LAS VEGAS, NV - OCTOBER 13: Democratic presidential candidates U.S. Sen. Bernie Sanders (I-VT) (L) and Hillary Clinton shake hands at the end of a presidential debate sponsored by CNN and Facebook at Wynn Las Vegas on October 13, 2015 in Las Vegas, Nevada. Five Democratic presidential candidates are participating in the party's first presidential debate. (Photo by Joe Raedle/Getty Images)
LAS VEGAS, NV - OCTOBER 13: Democratic presidential candidates U.S. Sen. Bernie Sanders (I-VT) (L) and Hillary Clinton take part in a presidential debate sponsored by CNN and Facebook at Wynn Las Vegas on October 13, 2015 in Las Vegas, Nevada. Five Democratic presidential candidates are participating in the party's first presidential debate. (Photo by Joe Raedle/Getty Images)
LAS VEGAS, NV - OCTOBER 13: Democratic presidential candidates U.S. Sen. Bernie Sanders (I-VT) (L) and Hillary Clinton take part in a presidential debate sponsored by CNN and Facebook at Wynn Las Vegas on October 13, 2015 in Las Vegas, Nevada. Five Democratic presidential candidates are participating in the party's first presidential debate. (Photo by Joe Raedle/Getty Images)
LAS VEGAS, NV - OCTOBER 13: (L-R) Democratic presidential candidates U.S. Sen. Bernie Sanders (I-VT), Hillary Clinton and Martin O'Malley take part in a presidential debate sponsored by CNN and Facebook at Wynn Las Vegas on October 13, 2015 in Las Vegas, Nevada. Five Democratic presidential candidates are participating in the party's first presidential debate. (Photo by Joe Raedle/Getty Images)
LAS VEGAS, NV - October 13: Bernie Sanders and Hillary Clinton pictured at the 2015 CNN Democratic Presidential Debate at Wynn Resort in Las Vegas, NV on October 13, 2015. Credit: Erik Kabik Photography/ MediaPunch/IPX
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The endorsement was widely expected. MoveOn encouraged Massachusetts Sen. Elizabeth Warren to run for president but when she declined last year many of its supporters got behind Sanders' campaign.

The group lists 8 million members and says it will mobilize nearly 75,000 of its members in Iowa and New Hampshire, which hold the campaign's first two contests.

MoveOn endorsed President Barack Obama during the 2008 primaries and helped rally Democrats in opposition to the Iraq War. The group was formed in response to the impeachment of President Bill Clinton, with its supporters urging Congress to censure the president and move on to more pressing matters facing the American people.

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