There were two options open to Vince Cable on his approach to tuition fees. The first was to battle for a credible series of concessions and support the policy that his Department agreed to. To some extent, he has achieved improvements on the existing system in the repayments schedule, but his failure to secure continued teaching funding for non-STEM courses suggests he didn't try hard enough. He had plenty of cards to play, but he chose to fold early on the final deal. Even so, he could still argue that as the minister responsible, he had a duty to support the final package. The other option is to argue that he made a solemn pledge to oppose a rise in fees - however daft that pledge was - and he should march into the No lobbies to oppose himself.
Had he chosen the first approach, with a clearer set of concessions and a fulsome apology for his party's stupidity and deceit to student voters, he may have retained some credibility. But by promising to abstain, then to vote for, then being not sure, and finally to vote for (probably) his stance looks absurd. All that is left is for him to borrow from Eamon DeValera in 1927 when he had to take the oath of allegiance to take his seat in the Dail, despite a solemn pledge not to do so. DeValera declared he was merely signing a piece of paper that had no meaning, except it allowed him to take his place in the Dail. Perhaps Cable could try the same logic on his bemused voters: he is merely voting with the Government as it allows him to take his place at the Cabinet table. It is no less credible than his shifting stances of the last week.