A prominent donor to the Democratic Party says she is considering withdrawing support for senators who urged their colleague Al Franken to resign after he was accused of sexual misconduct.

The donor, Susie Tompkins Buell, has been one of the Democratic Party’s most generous supporters for decades. In particular, she has been a champion of female politicians, including Senators Kirsten Gillibrand of New York, Elizabeth Warren of Massachusetts and Maria Cantwell of Washington.

Last month, those senators were among the dozens who called for Mr. Franken to resign from the Senate after at least six women accused him of sexual harassment or misconduct, such as forcible kissing and groping.

Mr. Franken announced his resignation on Dec. 7 before the Senate Ethics Committee had completed a review of the accusations, which he disputed.