America’s largest charitable foundation has quietly ceased backing a nonprofit network closely associated with the Democratic Party and criticized by conservatives, a symbolically significant blow to a powerful player in liberal politics.

The Gates Foundation decided in late June to halt making grants to nonprofit funds administered by the consulting firm Arabella Advisors, according to an internal foundation announcement reviewed by The New York Times.

That decision, attributed to the foundation’s chief executive, Mark Suzman, has sparked unease in the world of progressive philanthropy. Some nonprofits that work with Arabella are already seeking distance from the firm in order to preserve their relationships with the Gates Foundation, which primarily supports health initiatives around the globe.

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