Not too long ago, Representative Jerrold Nadler of New York confided in a friend about how he imagined his congressional career would end. He would like to go out, the person recalled his saying, like John Quincy Adams, who died in office after collapsing on the House floor.

Evidently, Mr. Nadler had a change of heart. The 78-year-old fixture of Manhattan politics announced on Monday that he would retire next year, giving a younger generation a chance.

The decision prompted a chorus of accolades. But this being New York, a city built on tomorrow’s ambition, it took less than 24 hours for the spotlight to shift forward to the once-in-a generation scramble to succeed him.

Eager young lawmakers dialed allies through the night. Powerful Manhattan Democrats, from the far left to the political center, dutifully tested the waters. Yet in a coveted Democratic district that is home to billionaires, chief executives, artists and political dynasties, operatives began compiling a roster of potential wild card candidates, too.

Some possibilities included Lina Khan, the former Federal Trade Commission chair and a young progressive favorite; Jack Schlossberg, a Kennedy in his 30s; and even former Representative Carolyn B. Maloney, Mr. Nadler’s contemporary who lost her seat in a redistricting showdown three years ago.

“It’s kind of unbelievable,” said Ken Sunshine, a public relations executive and longtime friend of Mr. Nadler, who called the district “a crown jewel.”