When to go?
A March election? Two advantages for Labour that I can see, and one disadvantage.
The first advantage is that, as Andrew Grice points out, it avoids the risk that Britain will be entering a double-dip recession just as a May election got underway. Given that the last quarter’s decline has just been gently re-evaluated up a touch, it must be likely that the next quarter will show the UK finally returning to growth. However, the forthcoming rise in VAT, coupled with the end of Quantitative Easing will very possibly tip it back under again. Running to the country beforehand at least avoids that possibility.
The second advantage is that Labour don’t have to have a budget. They can avoid both making spending cuts/raising taxes to reduce the deficit and increasing borrowing to maintain it – the choice doesn’t have to be made. Presentationally alone that is a benefit to Labour.
And the disadvantage? Labour are sinking quite a lot of effort into their ‘living will’ strategy whereby the Tories are hamstrung by existing Labour policies. Perhaps chief among these is the new 50p rate – it won’t raise any money, it’s unpopular with Tory voters and it will be a barrier to growth. Yet the politics of repealing it at a time of recession are extremely tricky. Yet if there is no Labour budget in April, then the new rate will never have been implemented. It is far easier politically not to implement a new tax than it is to repeal an existing one. By going early, Labour deprive themselves of their last opportunity to tie Tory hands. May (or June if things are really desperate) still looks like the best bet to me.