AFTER weeks of unofficial campaigning, we are formally off and running in the most unpredictable race to Number 10 in living memory.

And why is it so hard to call? Because there are fundamental questions hanging over all of the contenders.

David Cameron wants to complete the job of "turning the country round". The question for him is whether he can convince us that we really are all in it together as he pledges to continue his drive to cut the deficit.

Does he simply lead a party of posh people more able to absorb the impact of austerity? Does he care enough about those at the sharp end of the public sector cuts? Does he recognise the north-south inequality with which those cuts have been made?

Whatever the answers, Mr Cameron has at least looked like a credible prime minister – and that remains the biggest doubt facing his only real adversary, Ed Miliband.

Even in the Labour heartlands of the north, Mr Miliband has yet to be a convincing party leader and, as yet, not enough people are sure that he looks like a prime minister in waiting.

The Liberal Democrats, meanwhile, are due to pay a heavy price for their broken promises in being part of a coalition, and the inevitable question facing Nick Clegg is: "Why should we believe you this time?"

And as for Nigel Farage, can Ukip's protest vote appeal really translate into a general election or are they merely a bunch of narrow-minded fruitcakes who could never be trusted with the broad church of this great nation?

How well the party leaders respond to these doubts and questions over the next 38 days will go a long way towards deciding who runs our country for the next five years.