Is it an accepted form to begin a sentence with the word "neither" used as an adverb?
Many grammar sources discuss sentences beginning with "neither", but only in the context of the form of "neither... nor...".
Consider the following example:
Mr. Trump was unpopular among much of the electorate. Neither was he favored even by the established branch of his own party.
Note that little doubt seems to surround the following sentence:
Mr. Trump was unpopular among much of the electorate, and neither was he favored even by the established branch of his own party.