If you believe Grant Robertson's sales pitch for taking GST off fruit and vegetables, you’ll believe anything.

Because we know he has always been opposed to the idea. Today, though, he's saying he's “come around to the idea". Which is hardly a ringing endorsement, is it?

What he really means is he’s come around to the idea because Chris Hipkins says it's his way or the highway.

There might, I suppose, be some people who will want to believe that Grant Robertson has had some sort of moment of realisation. These will be the five or six people who think it’s a great idea.

But we all know Grant Robertson hasn’t changed his mind or had a change of heart. We all know that he’s been told by the boss what’s happening and he’s going along with it because the boss said so. And that his job as the party’s Finance spokesperson is to sell it.

The danger, though, for Grant Robertson personally is any credibility he might have built up during his time as Finance Minister may have just gone down the gurgler.

And for what? For nothing. Because this GST idea is not going to turn the tide on Labour’s fortunes.

The saving grace for Grant Robertson is that no one is going to believe him when he bangs on about it over the next few weeks and all the economists and tax people will know he still thinks it’s a stupid idea.   

And it’s a stupid idea that Labour should’ve ditched weeks ago. After National came out and said it had been tipped-off that Labour was planning a no-GST-on-fruit-and-veggies policy, Labour should’ve dropped the idea then because, straight away, all the people who know about these things wrote it off as dumb policy.

And they’re still writing it off as dumb policy. Which I think it is too.

Because, for me, what it comes down to is the opportunity cost of a policy like this. What you and I (collectively) will be missing out on for the sake of saving a few bucks a week. It’s an opportunity cost that couldn’t be starker.

It comes down to two numbers. The $5 that Labour reckons is the average amount of money most people would save by not paying GST on their fruit and veg. Versus the $2 billion that the government wouldn’t get in tax revenue.

That’s what it comes down to for me. I save 5-bucks. The government loses 2-billion bucks. You save 5-bucks. And we all lose 2-billion bucks.

2-billion less to spend on hospitals. 2-billion less to spend unclogging our courts system. 2-billion less to spend on roads. 2-billion less for schools. You name it. It’s just nuts.

We’re all feeling the pinch from what’s happened with the cost of living over the last few years and, for some people, even five dollars can make a difference. I know that. I get that.

But I just can’t see past the opportunity cost of stupid policy like this. Especially stupid policy announced two months from an election.

It is desperate. It lacks real thought. And it treats us voters like idiots.