By Henry Newman Sue Gray is carrying the can for the shortcomings and mistakes of her boss, says Henry Newman Morgan McSweeney is Keir Starmer’s second chief of staff following Sue Gray’s resignation. And we aren’t even 100 days into the new government. Some of his predecessors lasted far longer. David Cameron’s only chief of staff was there throughout his six year premiership. Tony Blair’s for a decade. Theresa May lost her joint chiefs after a year following her catastrophic election result. So for Sue Gray to be on her way out on day 94 is quite something. Whatever her strengths and weaknes…