When the American Israel Public Affairs Committee, the most influential pro-Israel group in the United States, wants to use its muscle, it can call on its considerable resources to run negative ads against lawmakers who oppose its agenda and pour money into funding a challenger.

When the Friends Committee on National Legislation, a Quaker group that is pushing for a cease-fire between Israel and Hamas, wants to push its message, its Middle East lobbyist turns to tactics like playing guitar with schoolchildren in the occupied West Bank and sharing video messages about their fears with members of Congress on Capitol Hill.

Going up against the many forces backing Israel is a challenge for any group. But the clash is especially striking when it comes to the Friends Committee, whose antiwar positions are in sync with much of the left of the Democratic Party but run counter to Biden administration policy in the wake of the Hamas terror attack and face intense opposition on the right.

AIPAC, founded about 70 years ago to promote Israel’s interests in the U.S., is a juggernaut. Last year, its nonprofit arm reported more than $73 million in revenue. Last month, its political action committee, which supports candidates who embrace its policy priorities, reported record fund-raising — bolstering a $40 million war chest that could be spent trying to defeat political opponents in Washington. It has the ear of congressional leaders in both parties.

The Friends Committee, which was founded during World War II, is part of what amounts to Washington’s peace lobby. It does not run a political action committee. It reports about $3 million in annual revenue. Its lobbying approach involves looking for “the divine in the people that we’re meeting with,” Sarah Freeman-Woolpert, the Quaker group’s deputy director of strategic advocacy, says in a video.