Senator Al Franken, Democrat of Minnesota, said on Thursday that he plans to resign “in the coming weeks” amid mounting accusations of sexual harassment against him.

Mr. Franken, 66, is from St. Louis Park, Minn. Raised in a middle-class household where education was emphasized, he went on to attend Harvard University. In 1969, he met Franni Bryson, his wife of more than 40 years, at a college mixer.

A comedian who spent years at “Saturday Night Live,” Mr. Franken reinvented himself as a politician before being felled by a string of harassment allegations in recent weeks.

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In 1975, he began a long career at “Saturday Night Live.”

After college, Mr. Franken and a childhood friend, Tom Davis, moved to Los Angeles to try their hand at stand-up comedy. Soon, they caught the attention of Lorne Michaels, who hired them as two of the first writers for “Saturday Night Live,” which began in 1975.