Norman Baker’s resignation as Liberal Democrat home office minister has refocused attention on the state of the coalition, just six months out from the general election.

Might we see a few more exits as polling day nears and politicians from both parties attempt to reclaim a bit of independence after four-and-a-half years in pragmatic partnership?

A lot may depend on when precisely the coalition is to come to an end. But we still don’t know when this will be. This is perhaps surprising, given how the government has tended to make a point of advertising its milestones and the scope (or limit) of its ambition. Yet the timing of the coalition’s demise is still a mystery.

One obvious date is 30 March 2015. This is when parliament is to be dissolved and the general election campaign will officially begin. After this date the business of government would continue but, given its representatives cannot be defeated in the House of Commons or Lords, there would be no need for the Tories and Liberal Democrats to be in a formal coalition. Ministers from both parties would remain in their posts, but purely in a procedural capacity. I’m sure they would be able to discharge their responsibilities until polling day in a spirit of professionalism, if not cooperation.

A date of 30 March means the coalition still has just under five months’ life left: plenty of time for a couple more resignations or dismissals to hint at a deterioration in government relations.

There’s always the chance things could fall apart sooner. But that would mean a bit of legislative horseplay in order to get the government’s remaining bills (and there are a lot of them) safely through parliament – chief of which would be George Osborne’s 2015 Budget.

The chancellor has yet to confirm when he will deliver his speech. The Lib Dems have reportedly pushed for the Budget to be brought forward from March to February to discourage Osborne from turning his speech into a shop window of pre-election giveaways.

There’s another reason why such a move would appeal to Clegg’s party, however.

Were the Budget to take place in mid-February rather than its usual berth of mid-March, this would allow it to complete its passage through parliament several weeks before dissolution. And once it was on the statute book, there would be little remaining reason for the Lib Dems to remain in coalition with the Tories. The party could begin a formal break-up in, say, early March, rather than having to trudge on in partnership right up to start of the election campaign at the end of the month.

It might be that the coalition has only four months left to run, not five.