Clark is the most powerful woman at the UN and is rumoured to want the top job.
Helen Clark has long been rumoured to have an interest in succeeding Ban Ki-moon as secretary-general of the UN in 2016. She was even criticised by the Guardian newspaper for being too openly ambitious. Due to factors such as nationality, gender and timing, she may very well be the front-runner.
The election of a UN secretary-general is a complicated process and takes place behind closed doors. Clark has much in her favour: serving her second term as head of the UN development programme, she is the most powerful woman at the United Nations and third most powerful person in the institution overall. She has made a few television appearances, raising her profile and a recent cost-cutting drive at the development fund may appeal to the UN's main Western donor nations.
Her nationality may also be quite influential. UN member states are semi-officially divided into five historically based regional groups - Africa, Asia, Latin America, Eastern Europe, and Western Europe and Others (WEOG). New Zealand is part of the WEOG group (essentially the old developed countries). The selection of the next secretary-general will be influenced, to a large degree, by perceptions of which region's "turn" it is to hold the post.
Traditionally, each region has rotated into the post for two five-year terms. The most "due" regions are the WEOG group and Eastern Europe. If she runs, Clark will presumably cite her "honorary European" WEOG credentials.
She would be faced with a number of potential rivals from Eastern Europe. Slovenia has nominated Danilo Turk, the former President of Slovenia. Slovakia has put forward Miloslav Lajkac, the Minister of Foreign Affairs, and Jan Kubis, a previous minister in the same office.
Here, timing and broader trends may again be on Clark's side. Momentum is growing for the next secretary-general to be a woman. In November, groups including Amnesty International and Global Policy Forum wrote to all UN member states stressing that, in the institution's near 70-year history, "no woman has ever held the post or been seriously considered for it". Clark would bank on gender trumping geography.
If the UN is determined to appoint a woman to the top job, there are several Eastern European contenders, including Lithuania's President Dalia Grybauskaite and Bulgarian European commissioner Kristalina Georgieva. Clark's biggest rival, however, may be a Bulgarian named Irina Bokova. She is the first woman, and first Eastern European, to head Unesco.
Bokova has not formally declared for the post, but has recently shown a greater interest in geopolitics, visiting Iraqi conflict zones, and a willingness to mediate in the Syrian conflict. A woman, as well as an Eastern European, she would seem to have a good chance come 2016 - but again, there are greater forces at work.
As well as having broad backing from the 193 UN member states, a candidate must be acceptable to the five council members with veto power: the US, Russia, China, Britain and France. An East European candidate must be acceptable to Russia, as it would be particularly picky about any candidate from the region it tries to influence and dominate.
That may give Bokova an advantage. She studied in Moscow and speaks fluent Russian. Russia's close UN Council ally is China, and Bokova has been diligent with this relationship, recently making the Chinese first lady, Peng Liyuan, the Unesco special envoy for the advancement of girls' and women's education.
Bokova was also Washington's choice for the Unesco post, but it's here that her candidacy might falter. She has since had several battles with the United States over Unesco's recognition of Palestine, which eventually led to the US withdrawing its funding entirely from Unesco in 2012. Her candidacy may never gain any real momentum given that the Americans could exercise a veto and push her off the shortlist.
Given all these dynamics, Clark's candidacy seems fairly strong; but there are further scenarios. A competition between Eastern Europe and the WEOG region could lead to the emergence of a compromise candidate from Latin America. Another potential snag is that few secretary-generals come up through the UN bureaucracy. Most are serving or just-retired foreign ministers. It's even feasible there could be a compromise to rotate the two European terms this round - allowing Bokova and Clark to serve one term each, like Boutros Boutros-Ghali and Kofi Annan did for the African region.
• Nick Sheppard is an author and political commentator.