He maintains he had good reason, but in the public's eye they weren't reason enough.

His resistance gave Labor an easy free kick - what did he have to hide?

Mr Abbott finally reneged and passed on the paperwork, only to have Treasury come back this week and declare the sums didn't add up. In fact, they were up to $11 billion out.

This is not a good look for a Coalition trying to prove its economic credentials to the independents who will decide who forms government.

No matter how they spin it, no matter how they try to sell it, Labor gets the better mileage. Another free kick.

The Coalition had claimed its policies would result in an $11.5thbillion budget surplus. Treasury says the figure is more like $863 million.

The difference comes about through assumptions. Treasury and the Coalition have both used a different set of economic assumptions to come up with two very different sets of figures.

That's probably correct, and the fact that the government would have had access to Treasury forecasts and the Coalition didn't is unfair.

Mr Abbott and his treasury spokesman Joe Hockey were desperate yesterday to sell the "surplus'' message.

While there are "differences of opinion'' between Treasury's figures and their own, both show a Coalition would deliver surplus budgets.

That's the message they were trying to drive home yesterday.

Whether the electorate buys it or not is irrelevant.

It is the independents Mr Abbott needs to convince that the numbers stack up.

And yesterday, at least one of them - Tasmania's Andrew Wilkie - sided with Julie Gillard.

Mr Abbott's bid to become prime minister just got a little bit trickier.