"like Bush, Blair is having to answer for someone else's sins"
Someone else's sins? If the allegations have any substance and there were cases where people were rewarded with peerages for donations that they had made to the Labour party, then I think responsibility for that might reasonably be said to rest with the leader of that party.
Especially given the position of Blair over what he portrayed to his great advantage as the 'sleaze' of the Conservative administration that he took over from!