Alistair Campbell was Tony'Blair's right hand man, but he was an effective sounding board and advisor who helped TB keep on such a popular path that he kept being re-elected and remained in power for thirteen years, winning three elections.
We don't know what advice AC gave TB about the Iraq war, which was his ultimate undoing. The Liberal Democrats did not vote for it but the Tories did. It then gave the Tories the opportunity to cash in in 2010.
We cannot compare AC's career as an advisor and strategist to Dominic Cummings who has, we are told, a temporary contract to work for BJ until 31st October and has so far done more than anyone to ensure that BJ is likely not to last much longer.