So many promises, so difficult to keep, such little time to decide. Liberal Democrat MPs now find themselves under intense pressure over how to vote on tuition fees.

Should they stand by their pledge to students, even if that means not standing by their coalition agreement with the Conservatives?

This morning, 104 Lib Dem Parliamentary candidates at the last election insist that it's the pledge that counts and that as a pledge it's worth more than a mere manifesto promise.

They say:

"This is not an attack on the Coalition Government's policy programme generally; nor is it some kind of 'rebellion' and it should certainly not lead to the party splitting. However we feel that this is a pledge that cannot be broken due to the nature in which it was signed and publicised during the 2010 General Election. This separates it from manifesto promises that have had to be sacrificed due to the concessions that coalition government brings."

So, a pledge trumps a manifesto promise - but what about an agreement?

The Lib Dems were laboriously consulted on the deal with the Tories. It explicitly stated that MPs could abstain if they didn't like the new coalition's policy - which, it was clear, would be an increase in fees. If they now vote against then why, some Tories might ask, should others stick by the agreement?

This is why Simon Hughes is seeking to persuade all colleagues that the only way to look like they're at least trying to respect the pledge and not breaking the agreement and to stay united is to collectively abstain.

The problem is that this would entail Vince Cable, the minister who's proposing the legislation, to abstain on it and it would require MPs, like Charles Kennedy, who've re-stated their determination to vote against higher fees to double-rat.

Another idea, anyone?

