At the 1924 Democratic National Convention, Franklin Roosevelt introduced New York Gov. Al Smith as the “happy warrior of the political battlefield." It’s been a popular pose on the campaign trail for more than 100 years since then, but another New Yorker chose to strike a different pose in his election night victory speech earlier this month. New York Mayor-elect Zohran Mamdani had a message for his political opponents. One was aimed at a former three-term Democratic governor, the son of an earlier governor who had long been hailed as a liberal hero, who lost to Mamdani first in their party’s primary and then a second time as an independent candidate in the general election. The other was directed at the president of the United States, a longtime New Yorker now serving a second, nonconsecutive...