Once in power, a Tory government will be tempted to be optimistic, to point to the sunny uplands. General Colin Powell said "positive thinking is a force multiplier" and the Cameron team come across as natural adherents to this viewpoint. There is also the fact that the modern Tory agenda - of decentralisation and trust in people - is at heart a positive philosophy of government, not a mistrustful statist one.
But President Obama has found that moving on, trying to focus on the future, being the Optimist-in-Chief has meant that US voters today blame his administration rather than George W Bush for the country's economic troubles. President Bush himself fared much better, spending much of his early days in the White House blaming Bill Clinton.
So, even if they win the election and are eager to get on with the business of government, there is good reason for the Tories to continue the blaming, to firmly (re)attach in the public's mind a view that Labour has been economically incompetent.
But for how long should this go on? Too much bile and blame won't work either. Taxes will have to rise and austerity measures introduced after the election. If these are presented by a permanently stern-looking, negative Prime Minister Cameron, the negative mood in the markets could be maintained for much longer. Too quick a switch will, however, also look odd and unbelievable.
So a Tory government will need a pivot. That may come in the shape of future recovery figures - about growth, inflation or unemployment. But one event - or even the run-up to it - could be turned into the point at which a new Tory government begins changing its message from one of blame and bother to one of determined if moderate optimism: the London Olympics. Lavish or on a shoe-string budget no other event has the power to be turned into a rallying point for the whole country.
Playing the blame game is good politics - even in the early stages of a new government but it is likely to be a bad long-term policy. So it will be key for the new incumbent in No 10 to find the right moment for a change in tone and message.