That sounds like it might be right. I think another commenter here correctly identified that it’s a misunderstanding -- Silver’s model estimates “the election result of the election were to happen tomorrow”, so unlikely events in the coming months don’t need to be accounted for by definition.

If so, I think there’s a valid criticism that the “now-cast” notion is a bit deceptive, and also impossible to validate (we’ll never know what that hypothetical election result would actually have been).

The nowcast does, but the nowcast isn't the main output, the two (polls-plus and polls-only) forecast models are.