NICK Clegg, leader of Britain's Liberal Democrats, knew this moment was coming and he dreaded it. In the closing days of the campaign, he would muse privately on his reluctance to take part in an exhausted, post-election scramble to form a government.

The politicians, he predicted, would be over-tired, overwrought and still antagonistic to one another, unable to think clearly. If they had to make a decision of such gravity, Clegg hoped they would be able to do so in a state of quiet calm, not in a panicked rush to cobble an administration together in time for the markets on Monday morning.

In this, as in so much else, the Liberal Democrat leader was to be disappointed. Denied the surge in support and seats the polls had promised, he lacked the clout to tell David Cameron, the Conservative leader, and the Labour PM, Gordon Brown, to calm down and get a good night's sleep. Instead he had to play fair maiden while the two suitors bowed before him, each offering a more perfect union than the other.

The result is that a sleep-deprived Clegg grapples with an excruciating dilemma. Only elected to parliament in 2005, it now falls to him to choose the next prime minister. Nearly 30 million votes were cast on Thursday but only one matters now it is up to Clegg to give the nod to what he used to deride as “the red or the blue team”. And whether he turns left or right, trouble awaits.

The appeal of a Conservative relationship — whether the flirtation of enabling a Tory minority government or the formality of marriage — is clear. Clegg always said he would deal first with the party with the most votes and seats, his definition of “a moral right to govern”. He can justifiably claim that a majority voted for change and therefore he is honour bound to install a new prime minister.

But the drawbacks are glaring. Too many Lib Dems — including big names such as Lords Ashdown and Steel — hint that they could not swallow an alliance with the old Tory enemy, so far apart on Europe, immigration and Trident missiles.

Millions of Lib Dem voters will feel the same way, howling that they didn't vote Clegg only to get Cameron.

Besides, and more crudely, Cameron hasn't offered Clegg enough — so far. All he pledged on the Lib Dem holy grail issue of electoral reform was an all-party inquiry. That's the most meagre form of promise in the political vocabulary. Perhaps it's an opening bid and will improve with negotiation.

Clegg can see the trap here. If he rejects Tory advances over PR, the Conservatives will slam the Lib Dems for putting their narrow, anorak obsession with the electoral system ahead of Cameron's much-vaunted “national interest”. That's the Tories' game to make Clegg an offer he'll look churlish to refuse.

If he looks leftward, he'll find a Labour prime minister all but gagging to do a deal, promising the earth on electoral reform. Some Lib Dems in Tory seats will object, but most would feel more comfortable with Labour than they ever would with the Conservatives.

— The Guardian, London