Judas Delegates?

Is the Clinton campaign waging a cloak and dagger campaign to persuade pledged delegates to switch sides?

She continues to rule in the possibility by pointing out that the DNC allows delegates to vote for anyone they want.

But the campaigns themselves file delegate slates. The delegates chosen tend to be extremely committed supporters. Many of them will turn out to be campaign volunteers and respected local Democratic offiicials who supported the candidate early. It is certainly possible to try and convince a pledged delegate to change his or her mind, but the universe of pledged delegates are probably the stickiest supporters a candidate has.