Welcome to the election. If we're to believe Alistair Darling, the Conservatives' 'credibility gap' on tax and spending has shrunk by 34% since January, or about £11bn. If they carry on like this, they might be thoroughly credible by election day.
Naturally, that is not how the chancellor put it in his press conference this morning, as he released more than 180 pages detailing the Conservative Party's (new and improved) "Credibility Deficit".
Back in January, Labour said there was a £33.8bn hole in the Conservatives' plans. Now it's fallen to £22.2bn - suggesting a 34% rise in credibiliy. But, to coin a phrase, Labour's numbers really don't add up.
I'll come back with more detail in a later post, but here are some of the headline problems which I spotted in the first few minutes of looking at it:
The new dossier claims that since January the Tories have "broken" promises worth £7.2bn a year by 2014/15.
But the promises they've broken aren't always the same as those listed in the January report. For example, back then, Labour said the Tories were committed to spending £5.2bn abolishing stamp duty on shares.
That has disappeared entirely from this report, to be replaced by an entirely new Tory pledge to reverse the abolition of the dividend tax credit (Labour's famous "pensions stealth tax") at a cost of £5bn.
I asked George Osborne's office about this. They said that he promised to "look at" abolishing stamp duty a few years ago. Apparently they looked at it and didn't like it.
And as for the dividend tax credit - well, he has said he wants to bring it back but in his conference speech he admitted that it could take "more than one Parliament". So much for that.
Back in January, Labour said Mr Osborne had promised to reverse the new 50p rate of income tax, at a cost £2.4bn. Now that's gone from the list entirely. It's not clear whether Labour thinks they "broke" that promise or not.
On the other "broken promises", the Conservatives have "broken" their promise of 45,000 new single rooms in the NHS. That's a fair cop.
Most of the other promises, such as reducing taxes on savings, were part of their submission to the 2009 Budget. Perhaps others will disagree, but it's not obvious to me they count as election pledges. If memory serves, there was some debate at the time about the status of the submission.
Likewise, the dossier itself provides no documented evidence for a pledge to spend £492m a year on providing maternity nurses for all.
The quotes in the report suggest that Conservative officials have said they will "look at" the system in Holland, which might cost that much to replicate here.
But even Labour's attack dogs don't seem to be able to find a solid Tory pledge to do so.
Two other big-line items are also on what you might call the flakier end of the "fact" spectrum.
Once again, the tax cut for married couples is listed at £4.9bn, which would be the cost of the change proposed some time ago by Iain Duncan Smith.
But the Conservatives have now made clear they will be recognising marriage on the cheap. It won't cost nothing. But it could cost less than £1bn.
You can call that derisory. You can say it's an empty promise. But you cannot then also say they've committed to spend nearly £5bn on it.
The document suggests the Conservatives will save precisely zero pounds from the efficiency drive announced this week, which Mr Osborne says will allow him to cut the budget of non-protected departments by £6bn.
Labour say this is because the Conservatives' savings are already included in the efficiency savings that Labour has already committed to for 2009-10 and 2010-11.
As I said on Monday, there is quite likely to be an overlap here between Tory efficiencies and Labour's. But there is one important difference. The Tories are promising to cut departmental spending in line with the savings.
That makes them "real", even if they are not as painless as they suggest.
If they are the same as the efficiencies already built into Labour's plans, then they will have a bigger effect on services than the Tories claim. But, once again, Labour can't have it both ways. You can't claim the cost-cutting will have a devastating effect on public services and the economy - but somehow, with all that, not raise any cash.
The Conservatives have at least given us a number by which to measure whether those savings happen. That is more than Labour has done.
And a party that has yet to account for two thirds of the £35bn in efficiency savings promised between 2008 and the end of this financial year (April 2010) isn't really in a position to lecture the Conservatives on their lack of detail.
There are other, more minor mistakes in Labour's document. For example, they have costed the National Insurance tax cuts for next year at £6.7bn a year - as if they were reversing all of next year's rise.
However, the IFS has estimated the cost of the measures proposed by Mr Osborne on Monday at £5.6bn a year, falling somewhat over time.
The bottom line? Well, I haven't read all 181 pages yet (forgive me). But right now I'm hard-pressed to identify a hole in the Conservative plans of more than £5bn, if that.
Now, you might see the gap between that and the Labour figure as a tribute to the slipperiness of Conservative "promises". Certainly, the document shows some nice sliding in the rhetoric of senior Tory politicians, between things that sound like promises, to aspirations, or vague "hopes".
They turn out to be "looking at" so many policy proposals - I'm surprised they have time for anything else.
Yet the Conservatives hardly have a monopoly on non-pledge pledges, or uncosted aspirations. This election campaign is already full of them, from all of the main parties. And it hasn't even formally started.
Labour may have planned to land a knock-out punch on April Fool's day. But, as far as the Conservatives are concerned, the joke may have backfired.