Texas.
Honestly that is pretty close to my guess. Still won't give Texas to Biden.
My prediction: Trump will declare victory, regardless of what the polls say, and hunker down in the whitehouse.
He will stay there directing efforts of lawyers trying to throw out any state's results where he lost by a thin margin, and get any friendly Republican controlled legislature to ignore the results of the polls and simply appoint Republican electors to the electoral college, resulting in at least one "dual" delegation.
He has telegraphed this move already.
It will be months before we really know the full outcome due to lawsuits.