I don't expect him to accept their offer. That would be foolish at this point. in time. But I would like him to be polite and acknowledge them.
But maybe I am wrong. All he could say is thanks but no thanks. By not answering he isn't saying no.
But the thing is there are stories about him from Vermont, that he ran Burlington very top down and also that in the state of Vermont as Congressman there was an iimplicit deal that the Democratic Party wouldn't back any viable contenders and he wouldn't support any viable third parties either. To caucus with the dems is to caucus with the dem.s
If I were I'm I would've answered something lie: Thank you for writing to us. As you know, we are running this campaign for the presidency under the Democratic PartyWe appreciate the work you do and share many common values. .Best regards, Bernie Sanders