The voting followed agreement with the majority Tories on the issue, under huge pressure to do so. If they'd disagreed they'd still have lost but not gained on the PR and House of Lords reform issues.If the Lib-Dems had voted against the increase it wouldn't have been passed. They sold out for a referendum on PR.
Those Lib Dem MPs who voted against that agreement were breaking it, not an honourable action and as said, pointless, since they could never have won. As we know with hindsight, the Tories were dead set on austerity, so would never have given way on the cost of abolishing tuition fees.
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