One of the many unfortunate things Vince Cable recently revealed to undercover journalists recently was that he actually boasts of what he called the 'nuclear option'. By this, he meant bringing down the Coalition. Its true that the prospect of the Liberal Democrats being pushed too far and walking out has always been in the minds of the coalition's architects and enemies alike. But now the tuition fees vote has happened, is that at all likely to occur?
For a start, the tuition fees vote has gone. There's unlikely to be another bill that splits the party as dramatically as the fees hike. If the AV referendum goes against them then discontent amongst social-democratic LDs might see a marked increase, but that alone isn't enough for them to safely use the 'nuclear option'. Without a big, dramatic justification for their action, the Liberal Democrats will come across as a party chronically incapable of government. Furthermore, without an emotive issue to act as a trigger I'm not entirely sure that the LD left could take the LD right out of coalition.
The critical factor being that if the Liberal Democrats were to withdraw and bring the government down, there would have to be a General Election. And who exactly would be voting for the Liberal Democrats in that scenario? Their left-of-centre support has largely evaporated and is unlikely to flit back to them the moment they leave office - the legacy of fees and being part of the 'ConDem' government will be too fresh. And their remaining (perhaps right-of-centre) support, consisting of those who approve of the job the LDs are doing in government and like how they're handling coalition, will probably follow the Conservatives. After all, if nice collegiate Mr Cameron is viewed as having treated the Liberal Democrats fairly and they still left, then it will sour the image of the party and coalition government in general in the eyes of a substantial proportion of their main supporters. In short, they'll be seen to have betrayed both halves of their pre-government support base, and their electoral strength could evaporate.
Furthermore, if as discussed above the social democrats try the 'nuclear option' without some compelling justification, there is a chance that some of their leaders might not follow them out. The likes of Nick Clegg, Danny Alexander and David Laws would have precious little incentive to follow their party out of the coalition in such circumstances, where they would be condemned to irrelevance-in-perpetuity within a permanently left-aligned party even if they didn't lose their seats outright. They could well see the logic in continuing in government, in coalition with the Conservatives.
From there, they could either do three things. They could become Conservatives, although this would probably lead to Danny Alexander not joining them and put Clegg's chances of holding Hallam in serious jeopardy. The second option would be to stand as independents with a non-compete deal with the Conservatives at the next election. The third would be to form a National Liberal style party/organisation that would remain distinct from the Conservative Party while continuing to be willing to ally with it whilst providing a home for other Orange Bookers and Liberals who might be uncomfortable in a solidly leftwing Liberal Democrat party.
Finally, one should not forget that Cable's stock has fallen hugely during the Coalition's time in office. Unlike 'Saint Vince' of those distant pre-coalition days, I personally doubt that Cable still has the personal pull to rip the Coalition apart and lead the Liberal Democrat left into the abyss I've outlined above.
If this happened, the Liberal Democrats would enter the subsequent General Election shorn of both credibility as a party and of any members who have earned any by distinguishing themselves in government. It would be a complete disaster. The left of the party is far better holding on for the full five years and trying to take credit for anything 'nice' the Coalition does, casting the Conservatives as the nasty lot. For these reasons, I think that Cable's talk of bringing down the coalition was egotistical bluster and not much more.