Manny Alicandro, a Wall Street lawyer and former stand-up comedian, was munching on salad at an Amsterdam, N.Y., steakhouse Monday when he learned that state Attorney General Eric Schneiderman had been accused of physical abuse by four women in a New Yorker article.

Mr. Schneiderman resigned hours later, leaving the race for one of the most powerful government positions in New York wide open.

“My jaw dropped,” said Mr. Alicandro, a 49-year-old Republican and political novice. He had only announced his candidacy that morning, officially declaring his intent to run at a sparsely attended event on the steps of Wall Street’s Federal Hall.

Mr. Schneiderman, a standard-bearer for the progressive wing of the Democratic Party who many considered a potential future governor, denied the abuse allegations but said they would prevent him from doing his job.

Mr. Schneiderman was the heavy favorite and presumptive party nominee until the abuse article broke.