The buzz is that National is about to back Auckland's CBD rail loop. And before you think the government's changed its roading stripes, let's consider the politics behind this

National parties and rail have long been, well, running on different tracks. But the buzz in Auckland this week has been that John Key may be about to jump the tracks (yes, I'm going to keep on with these puns) and come in behind the Auckland CBD rail loop. Now there's some news to that effect - that'll teach me for not writing this blog last night as planned!

This is quite a step for National, given not only the barely concealed scorn Steven Joyce and Gerry Brownlee have expressed for Auckland rail and the CBD loop in particular, but the anti-rail history of the party.

Sid Holland in 1949 put the kaibosh on public transport plans, as did Rob Muldoon in the 70s. Every time it looked like Auckland might get back on track, central government blocked the lines. (Though heck, while it's mostly been National, the fourth Labour government was the one that actually sold the railways and even Clark's crew spend three terms doing sod all, until it was too late).

It's as if the communal nature of rail somehow grated against National's individualistic politics; a person in a privately owned car, now that's for them. But I've heard Key is about to switch horses. [Ed's note: As, it seems, everyone has now, with the news everywhere. Really should've blogged last night].

It'll be a matter of Joyce and Brownlee swallowing some dead rats. Oh, they can say they always said a rail loop would come one day and so on. But they stalled, asked for reviews, stressed how "very, very expensive" it would be and insisted the case for funding had not been made. And Auckland was stuck, dependent as it is on some central government funding for such a massive project. National had the power and wanted to spend on roads.

So what's changed? Two things. Len Brown will win this year mayoral election without a decent National-friendly candidate standing against him. Brown will again spend weeks and months stressing that the rail loop is urgenly needed and his number one priority. He would have also spent that time sticking it to National and Aucklanders heading to the booths would have had that message firmly in mind.

What's more, agreeing to help fund Brown's baby helps ensure his re-election, something they would have been reluctant to do had Maurice Williamson or another ally been standing. But now that's not a problem.

Second, we're getting close to the next election and third terms are tough to win. National support will soften at some point (if only a little, if Labour can't get it's act together) and with coalition partners evaporating before their eyes, National strategists will be acutely aware of the Auckland vote. The polls will have told tham that Aucklanders want the loop and this change of stance gives Key a chance to say he's listening to the big city folk.

It nicely beats Labour while it's down and gives Aucklanders a feel-good factor now, but doesn't put the books at risk.

The government's surplus date won't be jeopardised by this spend, because the loop will be come years off, with most of the bill to be paid by a future government. But more than finances, this shift is about politics.

Here's Auckland councillor Mike Lee in 2010:

"...clearly this debate has got a fair way to run. But it would seem clear to me sooner or later if the Govt wants to be re-elected next year it will have to concede unlike the Puhoi to Wellsford Highway with its BCR of 0.4 – the CBD Rail Link does stack up. The Govt would dearly love to kill it off – but if they are not careful what comes roaring out of Auckland’s underground rail link could end up running down the National Govt.”

Well, he was one election out, but otherwise right in every sense. Just as Bill English has sucked up KiwiRail as a 'nice to have' he has to hang onto, so the Nats will suck up a bit more rail for the sake of the Auckland vote. And it could be a decisive blow, even more than a year out from the next election.

The inevitable looks set to finally become real. And what a relief for Auckland.