David Cameron must press home that only a Conservative government would deal with the deficit as a matter of urgency - unlike Labour or the Lib Dems
Just about everyone expected the deficit, the spending cuts and the tax rises needed to get the economy back on track to be the defining feature of this campaign. The great irony is that instead of engaging with the biggest problem facing the country, all three parties have shied away from it.
Now the Institute of Fiscal Studies has brought that omission into sharp relief, calculating the black holes in the parties' spending plans that will have to filled by a combination of tax rises and spending cuts.
It is a fair bet that the independent and authoritative IFS report will play a key role in the leaders' debate on the economy tomorrow night.
How should David Cameron respond? It is far too late for him to produce a shopping list of new tax rises or spending cuts. But he can seek to underline his personal commitment to getting the nation's finances back under control. He needs strong rhetoric to drive home the point that he has the will and the means to stop the UK going the way of Greece.
And, just as "New Politics" Clegg succeeded in lumping together "Old Politics" Brown and Cameron in the first debate, so the Tory leader can distinguish his approach from that of his two rivals.
He needs to drive home the point that only the Conservatives recognise the gravity and urgency of the crisis. Only the Conservatives will make an immediate start on balancing the books, unlike Labour and Lib Dem plans to delay action for another day. They are the mañana parties.
Cameron can couple this attack with a further stark reminder of the dangers of a hung Parliament. A Lib-Lab pact would bring together two parties with conflicting views about how to tackle the deficit but united on one point - a commitment to dithering and delay.
As Churchill would have put it, "they are decided only to be undecided, resolved to be irresolute, adamant for drift."
Cameron's other task is to pin the blame for the recession squarely on Brown's slumping shoulders. The last Conservative government left the economy in fine fettle. Brown's Labour government has left it as a basket case.
Nick Wood, Managing Director, Media Intelligence Partners