The election of a self-styled "liberal Conservative" as Tory leader should have increased the likelihood of meaningful co-operation between the two main opposition parties. But a perception that David Cameron "talks left but walks right" has fuelled Liberal Democrat suspicions about his modernisation project.
There are, in truth, only three policy areas where significant agreement could be reached: localism, education and civil liberties. On tax, the environment, criminal justice, Europe and constitutional and political reform, the parties are simply not on the same page.
It seems unlikely that the two parties could work together in a formal governing coalition. Nick Clegg won't rule this out before the election but he knows that to take his party into a Conservative-led administration, he would have to exact a political price (including a commitment to electoral reform) that Mr Cameron and his colleagues will never be prepared to pay. Furthermore, with no fixed-term parliaments, and the prime minister able to call another election at any time, the Lib Dems believe the political conditions needed to give a coalition even a fighting chance of survival are simply not in place.
But it would be a mistake to assume that the two parties will be unable to come to any agreement or understanding in the event of an inconclusive election result.
Why? The urgent task of avoiding a protracted period of political instability and uncertainty – a task that any market volatility in the days and weeks following polling day will make more urgent still.
Another reason is the Liberal Democrats' desire not to be seen to frustrate the democratic will of the people. If voters kick Gordon Brown out of the front door of No 10, Mr Clegg has no intention of letting him in the back door.
The Liberal Democrats, then, will find it difficult, if not impossible, to enter a Conservative-led coalition. But it will be no easier to revert to "business as usual" opposition. Whether they deal with a minority Conservative administration on a simple issue by issue basis, or enter into a more formal agreement – some kind of "confidence and supply" deal in which they promise to support the government in a number of key votes in return for policy concessions – they will need to act responsibly.
The party's leadership understands this only too well. The dangers of being seen to destabilise the government at a time of economic crisis significantly outweigh the short-term benefits of defeating the government on a series of Commons votes. In a hung parliament, the Liberal Democrats will wield significant political power but will have to use it sparingly. They will be an opposition party but in many ways will have to think and act like a governing party.
With politics set to be dominated for the foreseeable future by the need to tackle the UK's massive structural deficit, the overriding objective for the Lib Dems will be to demonstrate that they are part of the solution, not the problem.
Julian Astle is director of CentreForum. To read the report in full go to www.centreforum.org/publications/a-lib-con-trick.html