Will a coalition happen in Canada... or here?

On Tuesday the Canadian Parliament sits again, for the first time since the dramatic events at the beginning of December (When was this put to the electorate?, Has Canadian democracy triumphed? and Harper 1, Dion Nil ). In the weeks since then the Canadian Liberals have gone and done one of our Liberal Democrats' favourite things - decapitating their own leader. New leader Michael Ignatieff seems to be desperately searching for a way to get out of the proposed coalition with the New Democratic [sic] Party and the separatist Bloc Québécois - see Ottawa Citizen: Parliament vs. The People. It looks like for now Canadian democracy has triumphed, to the credit of Stephen Harper and the Conservatives.

But could such a situation happen in the UK? Just imagine if the next general election returns a hung parliament, as many have been speculating. And then if the Conservatives are the largest party but Labour forms a coalition deal with the Liberal Democrats and the Scottish and Welsh separatists (the way things are going in Northern Ireland it's doubtful there'll be any Nationalist MPs actually taking seats in the Commons), thus giving a strong say in the running of the country to those who want to tear it up. The big point of contention may be over what the parties say in the general election. If some or all of the parties give pledges against a coalition they could not credibly claim a mandate.

And if particular parties campaign against each other it will be especially galling. If the Liberal Democrats campaign to take a Labour seat on the basis that "a vote for the Conservatives is a vote for Labour" (supported by a dodgy barchart) they will be betraying voters if they turn round and put Labour in government anyway. When pressed on the question of what the party will do in a hung parliament the Liberal Democrats are frequently evasive, either talking about vague general goals or saying they won't answer the question until the voting system is changed. If they want voters to trust them, they should try giving a clear answer for the entire country for once. But that would be totally alien to the party's nature.