It's twelve years since National has had a knock 'em down and drag 'em out leadership battle.

It was when John Key knocked Don Brash down and dragged him out of caucus, even though the year before the former Reserve Bank Governor came within two percent of knocking Helen Clark off her perch. Politics is a tough, unforgiving game.

Since then, the National leadership's been rock solid and so has the party's support base.

But with Bill English gone and another leadership unknown about to be put in his place, that's all about to change. Any change of this significance always affects a party's popularity and it would seem only one of the five contenders can prevent that if you listen to the opinion polls.

The iron maiden Judith Collins is the preferred choice of National Party supporters and that's been fairly consistently around 44 percent of voters. But even though it should, public popularity won't decide who will step into Bill English's Hush Puppies tomorrow.

That decision will be in the hands of the 56 National MPs. But whoever it is, he or she's highly unlikely to win the next election. It's become a pattern in New Zealand for Governments to get two terms or more, ever since the one term Kirk/Rowling Labour Government in the 70s that achieved more in terms of reform than most Governments manage in three terms.

Word is that the best Collins can expect tomorrow is the deputy's job with 41-year-old Simon Bridges appearing to have the edge, but not yet enough to secure the job.

And with preferential voting, anything can happen in the ballots that'll be required until someone can reach the 29 votes required. That'll see support shifting from one candidate to another as the lowest polling wannabe drops off.

Over the weekend MPs have been bombarded with emails from their electorates telling them where to put their support.

Collins at the outset set herself a performance target of 35 percent if she gets the nod. She reasons that once a party falls below that level of support they're in trouble and whoever is the leader should start looking over their shoulder.

She's shrewd because if she is slotted into the deputy's job, as is expected, the target will be for the new leader and if they fall below it, who'll be laying in wait?

But then again, if Collins does win then she'll only have herself to blame.