"If Ebert had lived, his term as President would have come to an end on June 30 and even before his final illness he had indicated that he would probably not seek re-election." https://books.google.com/books?id=n0rWCgAAQBAJ&pg=PA191 And even if he did, why assume that he could beat Hindenburg? If the Weimar parties couldn't beat Hindenburg with a Zentrum candidate (Wilhelm Marx) they certainly couldn't beat him with a Social Democrat (they recognized this by abandoning Otto Braun for Marx in the second round).