Shelley B. Mayer, an assemblywoman from Yonkers, secured the Democratic nomination in mid-January. Ms. Mayer, a lawyer who has been in the Assembly since 2012, said she expected to benefit from the activism of Democratic women angered by President Trump. “The enthusiasm of women toward my candidacy — and toward women running in local elections — is extraordinary to watch,” she said.

The county’s Republican Party, meanwhile, has yet to name a candidate. Mr. Colety said that he hoped to nominate someone in early February. Neither of the two declared Republicans — Daniel Schorr and Sarmad Khojasteh — have held office, a fact that Ms. Mayer, 64, seized on. “I’ve been in the world of Albany, and I say it in a positive way because I know how to get things done,” she said.

Mr. Schorr was a prosecutor in Queens and Westchester Counties, where he specialized in sex crimes. (In 2009, he lost his bid for Westchester County district attorney) He also served as inspector general for Yonkers, conducting audits and investigations. Now he examines cases of sexual misconduct for Kroll, the private investigative agency.

A longtime resident of White Plains, Mr. Schorr, 44, said his experience would help him ferret out corruption in Albany. “I think our state is greatly overtaxed and corruption is part of that,” said Mr. Schorr, a graduate of Harvard Law School. “Every month for the next six months, there is a major corruption trial occurring in New York State.”

Mr. Khojasteh, a 36-year-old lawyer of Bedford, has made upward mobility a centerpiece of his campaign. The son of Iranian immigrants — he came to the United States when he was 1 — Mr. Khojasteh grew up in Poughkeepsie and attended the University of Chicago Law School.