Labour MP, and former leader, David Shearer has been shoulder-tapped to lead a United Nations mission in South Sudan.
That will prompt another by-election in a safe Labour seat which is a cost to the taxpayer.
But the bigger cost will be to the party which will lose another moderate MP
It won’t be a lot of fun going from Prime Minister to back bencher but John Key is staying in parliament so as not to trigger a by-election.
Retiring Labour MP, and another former leader, David Cunliffe, has also said he will stay long enough to not trigger a by-election.