I doubt it.
A show for liberals, by liberals, and made for liberals isn't going to have a republican president (even if it is played by Alan Alda).
That said, he has dropped hints that he isn't giving up his movie career for TV.
I'm not sure if Alda will be playing a GOP POTUS--I have never and will never watch that show. I do, however, love former GOP Senator Fred Thompson as the district atty on "Law & Order"--another very liberal show.