From Dictionary.com, a few definitions that may appear relevant
1. a solemn promise or agreement to do or refrain from doing something
5. something given or regarded as a security.
8. Obsolete: a hostage. [Hmmm!]
–verb (used with object)
10. to promise solemnly: to pledge one's support.
12. to stake, as one's honour.
13. to secure by a pledge; give a pledge for.
No suggestion of lying there but in future the electorate should remember that a pledge is as worthless as the piece of paper it is written on. That apart, the Lib Dems in the coalition have decided they must do the honourable thing and support the Government measure they are jointly responsible for.
But Mr Cameron is not out of the woods. What of his Big Society Agenda?
"It's about liberation -the biggest, most dramatic redistribution of power from elites in Whitehall to the man and woman on the street."
The students demonstrating on the streets would like to think so.