Under MMP, the party vote is the most important vote. It determines how many seats a party gets in Parliament, and hence who will form the Government.
So political parties all eagerly solicit your party votes.
However voters also get an electorate vote, and while this is of lesser importance than the party vote, parties still like to win electorates. Some purists suggest that parties should totally ignore the electorate vote, and only focus on the party vote.
But this overlooks a number of reasons why parties like to hold and win electorates:
The first is that electorate MPs are the official representatives of the local community.
They get invited to far far more community events, meetings with local Government etc. A major party with few electorate seats is less connected to the community. Labour partially struggles today because they have only 21 out of 70 electorate seats, just as National struggled after 2002 also with 21 seats.
Secondly many an MP's desire to hold an electorate is second only to Charlie Sheen's desire to have sex.
You might think many MPs would like not being an electorate MP, as they have less work to do. But to the contrary almost every List MP would love to be an Electorate MP. Some of them because they genuinely enjoy the advocacy work associated with being a constituency MP, and some because they see it as a secure power base where their re-election is not subject to the whims of the party's list ranking process.
A third factor is that Electorate MPs get greater parliamentary resources than a List MP. Around $25,000 of extra annual funding plus one extra Out of Parliament staff member. These can make a significant difference.
A fourth factor for minor parties, is that it ensures them representation in Parliament, should they get under 5%.
So which seats may change hands? Rather than just look at the 2008 election results, I focus on what the iPredict futures market prices are for a seat to change hands. If it is over 10c, or 10%, that suggests a reasonable probability. On that criteria the seats to watch are:
• Te Tai Tonga - Tirikatene (L) 76%
• West Coast-Tasman - O'Connor (L) 52%
• Tamaki-Makarau - Jones (L) 35%
• Te Atatu - Henare (N) 28%
• New Plymouth - Little (L) 28%
• Palmerston North - Hapeta (N) 26%
• Waitakere - Sepuloni (L) 24%
• Ikaroa-Rawhiti - Maori Party Candidate 21%
• Waimakariri - Wilkinson(N) 20%
• Auckland Central - Ardern (L) 20%
• Otaki - Foster (L) 19%
• Te Tai Hauauru - Peke-Mason (L) 17%
• Maungakiekie - Beaumont (L) 16%
• Waiariki - Other 16%, Te Kani (L) 10%
• Hauraki-Waikato - Maori Party Candidate 15%
• Rimutaka - Fletcher (N) 13%
• Ohariu - Chauvel (L) 13%, Shanks (N) 11%
• Hamilton West - Moroney (L) 12%
• Rangitata - Other 11%
• Mana - Parata (N) 10%
• Port Hills - Carter (N) 10%
• Te Tai Tokerau - Davis (L) 10%
So there are only two seats where at this stage it is expected to change hands (over 50%). Then there are another eight seats which have a 20% or greater probability of changing hands. And a further 12 seats with a 10% to 19% probability.
It is interesting that Te Tai Tonga and West Coast-Tasman are both rated so strongly to change, despite the lack of any public polling in those seats. As the election gets closer, I expect we will see local newspapers commission a number of polls in competitive seats.
Shane Jones is now rated the third most likely person to win a seat, based no doubt on the likely entrance of Willie Jackson for Mana into the race.
What is fascinating is that in the next lot of three seats, two of them are potential pick ups for National. It is rare for incumbent Governments to win additional electorates but Tau Henare is ranked 28% in Te Atatu and newcomer Leonie Hapeta 26% likely to win Palmerston North - the sole remaining provincial seat held by Labour in the North Island.
Both major political parties face tactical decisions with these marginal electorates. How much money and energy do you spend on defending your vulnerable seats, how much do you spend on trying to win news seats, and how much do you spend on the more important party vote campaign. It can be a difficult balancing act.
* David Farrar is a centre-right blogger and affiliated with the National Party. A disclosure statement on his political views can be found here.