There are of course more than three possible futures for the Liberal Democrats and their wretched pickle about tuition fees.
But here are three futures:
Future 1: "The best policy in the circumstances"
Nick Clegg, Vince Cable and several Liberal Democrat members of the Coalition Government vote in favour of the bill on tuition fees, having wrung a couple more concessions from the Conservatives, and having abstained on an artificially-created and largely symbolic Commons vote relating to the level of the cap. The rest of the ministers and a few backbench MPs abstain (as allowed by the Coalition Agreement). The majority of backbench MPs vote against. The bill goes through.
Some commentators and students eventually acknowledge the benefits of the policy over the current situation, and there is scepticism about the role of the NUS, but the failure to honour personal signed pledges overrides all. The whipping of MPs on a bill that goes against party policy enrages the party membership, but the Coalition continues, with the Liberal Democrat Party's credibility severely weakened. The AV referendum is lost in a petty anti-Clegg vote. Within the government, liberal values are crowded out by authoritarian influences.
Clegg is consequently ousted in 2012, but the 2015 general election ends in disaster with MPs in university constituencies wiped out, whether they kept their pledge or not, and despite the Liberal Democrats being the only party with a policy to abolish tuition fees. Under FPTP, Labour forms a majority government with 41% of the vote.
Future 2: "The price of stable government"
Pressure from the grassroots, backbenchers, and ministers in vulnerable seats leads to a collective decision to abstain on the bill. However nearly all backbench MPs vote against the bill, along with some ministers, who resign from the Coalition Government. The bill falls, leading to an immediate motion of No Confidence.
This fails, and crisis talks between David Cameron and Nick Clegg eventually result in an agreement to continue the Coalition Government, provided there are no more such rebellions. The AV referendum is won, and a liberal government makes good progress in relation to civil liberties, social justice and climate change. However Nick Clegg's standing within the party is severely damaged, resulting in a leadership challenge in 2012.
He survives, and in the 2015 General Election the Liberal Democrats are seen as the plucky terriers who stood up to the Tory rottweilers and won. Enough additional seats are won to form a LibLab Coalition.
Future 3: "For the good of the party..."
The grassroots get organised enough to threaten the deselection of MPs who fail to honour their pledges. This, combined with plunging opinion polls and a sense of duty to their voters, causes the parliamentary party to present Nick Clegg with the fact that they cannot in good conscience do other than vote against the bill. Clegg argues fiercely that a renegotiation of the Coalition Agreement is impossible, but an impasse is reached. Clegg resigns.
The interim leader, Simon Hughes, presents the party's view to the Prime Minister. David Cameron notes that it would be a breach of the Coalition Agreement for Liberal Democrat ministers to vote against the bill, and should any do so they must leave the Government. The party votes overwhelmingly against bill, with Nick Clegg, Vince Cable and a few ministers abstaining. The bill falls, and Cameron calls an immediate General Election.
The Liberal Democrats are portrayed in the campaign as weak, divided and lacking the maturity to govern. Since the AV Referendum has not been held, the FPTP system applies, and the Conservatives form a majority government with 38% of the votes.
Warning: I am notoriously unreliable when it comes to predictions. Nevertheless, I love making them, because they help test the strength of my understanding of current political circumstances and of the variability of the factors affecting the future. This does have the consequence that I'm wrong a lot of the time! And certainly less to be relied upon than analysts who make few predictions, or vaguer ones.
At this moment in time my gut reaction is that the three futures described above are in descending order of likelihood. But I'm interested in hearing about alternative futures.