Too early. They want as little time as possible to vet the replacement candidate.
Good analysis.
Also the ridiculously fickle American people gush over and adore a new face for about 2-3 weeks and then are bored and toss them aside. Former Mayor Pete was the thing, Bernie had the "Bernie's Bern" surge going, watch out for Elizabeth Warren to take it all except Mike Bloomberg was the chance to win big in November....Where are they now?
If they can rush in Cuomo at the last minute and dress him up like they did Obama: you know, that Brilliant-Savior-of-the-World-in-Greek-God-Garb--or like they did Hillary: The-Smartest-Woman-in-the-World-Who's-Also-Selfless, Caring, Elegant, and Classy (nevermind the filthy language)--that sort of thing--they can overwhelm the Lower Slobovia voters with propaganda and, who knows, pull off an upset???.
I don't know why I didn't think of that.