Nick Bryant in the NBR today laments the fact that "the current splitting of the vote on the right is causing Act and the right serious harm", and pins the blame squarely on United Future. He demands that United Future either merge with National or publicly renounce the possibility of coalition with Labour - which just goes to show that a) he's arrogant; and b) he doesn't understand MMP.
While Bryant refuses to recognise it, there clearly is some difference between United Future and National. It's hard to imagine the latter supporting assistance to first home-buyers or the government's "Working for Families" package, for example. Instead, National's policies are dominated by its right wing. But while United Future would clearly belong in the National Party - they're in pretty much the same position as centrist National MPs - there's a very good reason for them not to merge: they have more power seperately than they would if subsumed into a larger grouping. As a seperate party, they are accorded an independence that would not be granted to a group of centre-leaning MPs.
Questions of power aside, Bryant is demanding that anyone who leans vaguely right should shut up and let the extremists dominate, rather than advocating their own position. That's the sort of arrogance you expect from those on the left who try and bury dissent beneath "solidarity". But it also shows that he does not understand MMP. Under MMP, wing parties are not the "vote stealers" they are under FPP systems. Voters switching between parties in a faction (say, from Labour to the Greens, or National to ACT) do not affect that faction's overall share of the vote or ability to form a government. To the extent that United Future has common ground with National, then, vote-splitting on the right does not affect National's ability to govern. And this exposes Bryants real beef with United Future: they don't have enough common ground with National (or rather, with the right-wing faction that is currently dominant), and b) National has no ability to govern anyway - the right's share of the vote simply is not big enough. He's just lashing out in impotent frustration at the thought of neo-liberal policies being rejected yet again (as they have been in every election since 1990).
And while I'm at it: if Bryant was seriously concerned about ACT, he should advocate for abolishing the undemocratic, distorting threshhold - or rather, reducing it to 0.8% (the level required to get a single MP). That would allows ACT's support to stabilise at it's natural level of around 2%, without the worries every election about them being evicted from Parliament.