Yes, it does matter that Labour makes the change

Steve Richards goes through all the hoops regarding Brown’s leadership having “spoken to ministers, special advisers, MPs and other senior Labour supporters in recent days”.  After he goes forwards, backwards and sideways we get to the important point:

I am told that Mandelson cannot envisage Johnson rising to the huge demands of being Prime Minister and does not feel David Miliband is ready yet.

We can forgot Miliband.  However, the role of Mandy is key.  Without him on board, as discussed previously, it is doubtful that a successful transition can be made to Alan Johnson without Labour tearing itself apart.

However, he doesn't conclusively say that a change will not happen:

If the polls are still terrible for Labour after the conference season something dramatic might happen. No one knows for sure. One Cabinet minister tells me there will be no successful coup but that it is just possible Brown may decide to quit.

Then:

In my view this is the one possible alternative route, a voluntary departure. It is still unlikely and an uncontested coronation of Johnson would leave all the unresolved problems. Let us not forget Labour was miles behind in the polls in the final years of Blair. The reasons for the party's unpopularity are deep and a change to an untested leader in advance of an election will not address them.

In a way Richards is right.  The change to “an untested leader” will not address the party’s deep-seated problems, but it may well stop a catastrophe at the polls and all that will flow from that.  It could even mean a hung parliament.  Remember the swing that the Tories need.  That is way it is worth making the change.

The debate the Labour party needs to have is for later, not six months out from an election.