NEW YORK (AP) — U.S. Rep. Max Rose, a first-term Democrat who lost his reelection bid last month, said Sunday he is exploring a run for mayor of New York City.

“The five boroughs are where dreams are made, underdogs triumph, and anyone can build a better future,” Rose said in an email to supporters announcing that he is exploring a mayoral campaign. “Yet that New York is slipping away, and for too many, it’s already gone. With so much at stake, we can’t sit on the sidelines.”

Rose, 34, is an Army combat veteran who defeated incumbent Republican Dan Donovan in 2018 to represent a congressional district that includes all of Staten Island and a slice of Brooklyn.

Rose lost a hard-fought 2020 race to Republican Nicole Malliotakis, a state Assembly member. A centrist Democrat, Rose ran campaign ads criticizing current New York City Mayor Bill de Blasio as anti-police during his reelection bid.

Rose registered his mayoral campaign with the city Campaign Finance Board on Thursday.

If he joins the 2021 race to succeed de Blasio, who is term-limited, Rose will have to compete with a crowded field that includes City Comptroller Scott Stringer, Brooklyn Borough President Eric Adams, former U.S. Housing Secretary Shaun Donovan and former de Blasio counsel Maya Wiley. Former tech executive and Democratic presidential candidate Andrew Yang has been meeting with civic leaders in advance of a possible mayoral campaign announcement.