Within minutes of Sen. Chuck Schumer’s announcement Thursday night that he will oppose President Obama’s nuclear deal with Iran, progressive advocacy group MoveOn — which has been lobbying in support of the deal — urged its eight  million members to withhold campaign contributions from Democratic candidates against the deal.

[Sen. Charles Schumer opposition to nuclear deal may bring other Dems with him]

 Sen. Chuck Schumer (D-NY) announced Thursday night that he opposed the Iran nuclear deal. (Photo by Matt McClain/ The Washington Post)

The group’s “Democratic Party donor strike” aims to secure commitments from its members to withhold $10 million in contributions from lawmakers and party committees. That figure is not what MoveOn as an organization would withhold from candidates and committees, but rather what individual MoveOn members would potentially withhold collectively.

“We will organize grassroots progressives across the country to withhold campaign contributions from the Democratic Senatorial Campaign Committee and from any Democratic candidate who succeeds in undermining the president’s diplomacy with Iran,” MoveOn said in a statement. “Our goal will be to secure commitments to withhold $10 million in contributions within 72 hours after this campaign launches.”

MoveOn is known more for its grassroots organizing than for being a major political contributor. In the 2014 election cycle, MoveOn gave $125,000 and bundled $644,160 for House and Senate Democrats. In the 2012 cycle, the group gave $701,634 and bundled just over $4.5 million — $2 million of which was for Sen. Elizabeth Warren (D-Mass.) — for House and Senate Democrats, according to the Center for Responsive Politics.

A number of Democratic lawmakers who received MoveOn contributions in the 2014 cycle have already come out in support of the deal, or appear to be leaning toward doing so, including Sens. Warren, Mark Udall (D-Colo.) and Jeanne Shaheen (D-N.H.).

[Groups supporting Iran deal face off against its deep-pocketed detractors]

The donor strike is the latest tactic MoveOn is taking in its campaign to see the nuclear deal survive a congressional vote. The group has committed to spending six figures on radio, television and online advertising, and is hiring more field organizers in a several states to encourage lawmakers to stand behind the deal.