Simon Bridges is believed to be ahead in the National Party leadership contest but is still short of the numbers required and at risk of being overtaken if the vote by National's MPs goes into a second round of voting.
The winner next Tuesday will need at least 29 votes out of National's 56 MPs to secure the role.
It is increasingly doubtful any of the five contenders - Bridges, Amy Adams, Steven Joyce, Mark Mitchell and Judith Collins - will get to the magic 29 before the vote, although a substantial number of MPs appear to be still undecided.
The candidate who gets least votes is eliminated and further ballots are held until somebody gets to 29.
That has meant the candidates have had to lobby strategically to try to secure pledges for the second-round votes of those MPs backing a rival.