Tauranga MP Simon Bridges is looking forward to tomorrow's caucus meeting in Wellington, where the National Party MPs will vote on who will replace Bill English as party leader.

Simon was among the first MPs to put his hand up nearly two weeks ago for the role.

He will be up against the party old guard of Judith Collins and Steven Joyce, as well as relative newbies Amy Adams and Mark Mitchell.

'I'm excited about tomorrow,” says Simon. 'It's a great opportunity to lead the National Party and make a real difference. I feel good about my level of support, but of course there's four other quality candidates, so I can't take anything for granted.”

He says he and his caucus colleagues will meet around 10.30am, where a vote will be held on both the leader and deputy leader positions.

The voting system is progressive, meaning if no candidate secures a majority of caucus outright (29 votes), the lowest-scoring candidate will drop out, and another round of voting will commence.

Although there are five MPs vying for the leadership, so far only Paula Bennett has indicated an interest in the deputy role.

'Ultimately it's for caucus to decide,” says Simon. 'Paula is our current deputy, and I could certainly work with her.”

He says if he doesn't win, he'll be disappointed, but intends to get in behind whoever is leader and make sure National is an effective opposition.

He's also ruled out taking another tilt at the leadership before the 2020 election.

'National doesn't replace its leader very often,” he says. 'Tomorrow's leader will be only the 12th in history, while Labour has gone through several in the last few years. So I think we have a good system in place.”

Jacinda Ardern is currently the Labour Party's 17th leader – although previous Labour Prime Minister Helen Clark was the 12th.

Helen was also the longest-serving Labour Party leader, at just shy of 15 years, while the longest-serving National Party leader was Sidney Holland, at a staggering 17 years.

Jim McLay has the distinction of being the shortest-serving National leader at around 16 months, while David Cunliffe served the shortest term as Labour leader, at just over a year.