It's not exactly a sign of being a great leader, is it?
A real leader and statesman would have taken measures to ensure it could never happen. The fact that Blair didn't do that shows why he can never be regarded as a great Prime Minister.
If you think I am being a bit harsh, imagine if a company chief executive deliberately allowed a successor to taake over who he knew would bankrupt the company. It just wouldn't happen, would it? The chief executive would make sure the board of directors didn't make such a disastrous decision. He would speak out, wouldn't he/she?