There’s concern that Mamdani’s selection could prompt the Dems to lurch to the Left (US “left”, not actual left) thinking that is what the country want, and that didn’t work too well at the last election. New York is liberal, but most of the country is not and it could play into the “coastal elites” narrative.
They talked a bit about it on yesterday’s live TRIP US and mentioned that another Democratic Primary recently (in Virginia I think) had gone with more a traditional “centrist” Democrat, so they need to be careful not to jump to conclusions.
That said, he’s a really interesting guy with lots of good ideas. He did an interview with Pod Save America a few weeks ago which is worth listening to.
Its in the second half of this episode: https://podcasts.apple.com/gb/podcast/pod-save-america/id1192761536?i=1000712699407