Yes, there are some big states among the 27 that have not yet voted, among them Georgia, Ohio, Pennsylvania, Wisconsin, Maryland, New Jersey, and New York. (Cuomo recently announced that his state’s primary, previously scheduled for April 28, will now take place June 23.) But Biden already has 1,215 of the 1,991 delegates required to clinch the Democratic nomination. Sanders has 909. There aren’t enough delegates up for grabs in remaining primaries for a new candidate to win.
Plus, apart from a write-in campaign, to allow Democrats in those states to vote for Cuomo would take throwing out all the party’s rules — the rules Biden, Sanders, and the rest played by. And, of course, voters in the majority of states and territories that have already voted would never have the chance to consider Cuomo. Finally, even if all the rules were magically changed, the idea of Cuomo abandoning his current job at this critical time to run for president is nuts.
So the only way any Democrat could seriously hope for Cuomo as their presidential nominee would be a convention in which delegates threw out Biden, and Sanders, and started from scratch. And that would obliterate the fundamental principle of the candidate selection process: The nominee should be selected by the party’s voters. It is simple, straightforward, and sacred.