He dragged the Labour party into government by widespread changes which manifested as "New Labour" winning power in 1997 and they managed to hold power for 13 years. He handed over the reigns to Gordon Brown a couple of years before their election defeat in 2010. In a way he made them into an election winning party, but as with all long term governments they lost their gloss and direction and there were huge questions over them dragging us into the Iraq war. So yes, his and browns legacy eventually ment the Labour party had to reinvent itself to escape the spectre of "Blarism", but he was a huge part in them being in power so long in the first place.