After two weeks' lobbying, Tauranga MP Simon Bridges is still well ahead in National's five-way leadership contest.

But Amy Adams could still beat him if she picks up more support when Judith Collins, Mark Mitchell and Steven Joyce, as expected, drop off the ballot in tomorrow's progressive vote.

Voting will continue in rounds, with the lowest-scoring candidate dropping off, until a candidate reaches 29 votes out of a caucus of 56 to replace Bill English.

Several camps report that Mitchell's soft support has fallen off over the weekend although he has not conceded that.

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He rejected a suggestion he could drop out saying he was "in it to win it".

One of the biggest issues is whether candidates are counting only promised votes or soft support as well in their totals.

Adams is understood to have been in discussions with Steven Joyce over the weekend, although like Bridges, Adams has said no deals will be done before the vote on jobs.

Joyce is thought to have picked up some support - Louise Upston joined chief Joyce lobbyist Nathan Guy over the weekend to seek support for the former Finance Minister and party strategist.

No one other than Joyce says he can win. But he is more likely to have a prominent role under an Adams leadership than Bridges, possibly even as deputy leader or keeping finance.

A separate deputy leadership vote will occur soon after the leadership vote - which is likely to be a woman if Bridges wins and a man if Adams wins.

While Bridges is not running on a ticket, he has all but endorsed Paula Bennett to continue in the role.

However if Bridges wins, Judith Collins could put her name forward as deputy, and it is a secret ballot so there are no guarantees of who would win.

Joyce indicated he would not walk away if he failed to become leader, or even if he failed to keep finance.

"I'm very keen to be the leader. I think I have the skills that will help us succeed in 2020 and more important help New Zealand succeed if we win the 2020 election.

"But I don't think anyone should be in the situation where they say 'well I'm not prepared to contribute in any other way.'"

He said not a single person had raised concerns with him about the amount of power he had acquired over the years as party strategist, then finance minister.

Judith Collins, with little support in the caucus, has fought her way into a big role in the new line-up after Tuesday's election, having harnessed the support of party members into a lobbying campaign of local MPs in support of her.

Neither the Bridges nor Adams camps is contemplating a loss and the possibility of becoming deputy leader to the other.