As of 20 August 2017 the Labour Party overtook the National Party in terms of Facebook likes, a position they hadn't been in since 22 September 2014. At it's height, the gap between the two parties was around 18,000 page likes, as at the time of writing Labour is now approximately 400 likes ahead. Having been 200 ahead overnight.
National has enjoyed two significant boosts in the past year, in September of 2016 and from December through to January 2017 following Sir John Key's resignation and Bill English becoming leader and Prime Minister.
Labour's two boosts are from Parliamentary paid advertising just before the three month Regulated Period kicked in, and then from Jacinda Ardern becoming Labour leader at the start of this month.
When you look at party leaders over a similar period (unfortunately my analytics tool can only pull data from September 2015 for most of them) you can clearly see the moments Bill English became Prime Minister and Jacinda Ardern became leader of the Labour Party.
Jacinda's rate of growth is now trailing off from the initial boost she received, but she's still growing by about 3,200 page likes more than Bill English each week. Assuming the rate of growth over the past week is more indicative of the campaign period itself, Jacinda will be just shy of 100,000 page likes by the election, while Bill will be around 107,000. Looking back at 2014's data, neither John Key or David Cunliffe seemed to enjoy a bounce from debates, but then again those debates didn't set the world alight, so a clear debate win for Jacinda could make a big difference for her.
As I've mentioned before, Facebook page likes aren't going to win you an election, but insofar that the more you have, the more people you can reach, and the morale boosting effect of knowing you are more popular than your opposition will have some impact on how you perform.
If you're curious where we sourced our data and graphs from from check out Quintly. It's an easy to use social media analytics tool that takes a lot of the hassle out of visualising your social media data.