National MPs have a difficult choice because they have to decide whether their prospects of winning the next election are better served by offering continuity or change.
Joyce and Adams, as high ranking ministers in the previous Government, represent continuity.
Collins, Bridges and Mitchell in their different ways offer change.
Collins is offering a change of both style and substance. Her style is direct, confrontational, uncompromising and she would reposition National with a conservative emphasis after the liberal directions taken by English and Sir John Key.
Bridges offers generational change, by which he means more than his youthful physical features. He is expressing "blue-green" concerns hitherto unsuspected in a former Energy Minister who argued for oil exploration. Mitchell, the least experienced MP in the field, offers a clean slate to the public.
Normally there would be no question a party relegated to Opposition would be looking for change.
But National has not lost power in the normal way. It is the largest party in Parliament and its economic record is enviable. Under Joyce National would be a constant and credible check on the Government's economic and fiscal performance.
Under Adams the party might make more compromises with the Government's direction.
History says that unless the Government is very unlucky, or makes some big economic mistakes, it will probably be re-elected at least once. The odds will be against National's next leader winning the 2020 election whoever the MPs choose.
For the younger contenders this leadership contest might be a good one to lose. They have put their name into consideration for the future.
They could withdraw this time, perhaps settling for the post of deputy to Joyce or Collins, or the finance role.
Collins would be the favourite if National's core supporters were making the decision.
Many of them say they like her style and would welcome a more combative Opposition.
National's MPs might not be so comfortable with it but they need to make up their collective mind, preferably before Tuesday.