Updated 12:14 a.m. | Did Sen. Charles E. Schumer just open himself up to a serious challenge to lead Senate Democrats in 2017? Top allies of the president say yes — and a major liberal advocacy group now wants him gone.

MoveOn.org announced a “donor strike” after the New York Democrat’s announcement that he opposes the Iran deal and compared him to Joseph I. Lieberman, while former senior White House aide Dan Pfeiffer warned the Democratic base wouldn’t support Schumer for leader.

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MoveOn said its 8 million members will withhold funding for the Democratic Senatorial Campaign Committee and from any Democratic candidate who sides with Schumer.

“While not unexpected, it is outrageous and unacceptable that the Democrat who wants to be the party’s leader in the Senate is siding with the Republican partisans and neoconservative ideologues who are trying to scrap this agreement and put us on the path to war,” said MoveOn.org Political Action Executive Director Ilya Sheyman in a statement.

“Our country doesn’t need another Joe Lieberman in the Senate, and it certainly doesn’t need him as Democratic leader. The vast majority of Democratic voters — the people who elected President Obama in part because of our shared belief that war must always be a last resort — will not stand for it.”

And Pfeiffer’s tweets were brutal.

Senator Schumer siding with the GOP against Obama, Clinton, and most Democrats will make it hard for him to lead the Dems in ’16

— Dan Pfeiffer (@danpfeiffer) August 7, 2015