Are David's little helpers about to go large?

The Independent is reporting that the Conservatives and Liberal Democrats are toying with the idea of a pact in the event of a Yes vote in the AV referendum, meaning that each party would urge its supporters to give a second preference vote to the other -

"Some Tory MPs are advocating such an agreement to keep Labour out of power. Although Liberal Democrat MPs are more cautious, they admit a pact would be a possibility if the Coalition proves successful."

Have these Lib Dem MPs even taken ten seconds to think this through? The only thing that could begin to make it worth their while to agree to such a deal would be a commitment from the Tories that the coalition would continue regardless of whether they won a majority in their own right - and yet history shows a coalition in such circumstances is barely worth having for the junior party. The reason? Quite simply that the Lib Dems would have no bargaining power left at all - it would be a coalition that stands or falls entirely at the Tories' discretion. The two parties could draw up the most solemn and theoretically binding partnership agreement in the world, but the Lib Dems' own betrayal over tuition fees shows just how much such commitments are worth once the cold reality of the parliamentary arithmetic makes itself felt. If the coalition breaks up in this parliament, the Tories know they risk losing power instantly - but what would they be risking by breaking a coalition deal if they had a majority anyway?

The paradox is that, under AV, urging Lib Dem voters to give a second preference to the Tories may well - at least in some circumstances - make a meaningful coalition less likely, and a Tory majority that would freeze out the Lib Dems far more likely. The phrase "David's little helpers" is already rather apt, but I trust they wouldn't be so tactically inept as to take the assistance to this gratuitous new level.