It’s a natural human condition that once someone makes a decision it’s practically impossible to get them to change their minds and persuade them they were wrong.
But that’s exactly what you’re asking voters who voted for your incumbent opponent in the past to do.
Take this to heart: You’re not asking those people to simply hire you. You’re asking them to admit they made a mistake and fire the other guy. A much higher threshold.
You could be the greatest candidate since Reconstruction, but unless you give a voter an “out” to excuse the mistake they made the last time (or last several times!), you’re unlikely to get them to change their minds and vote for you this time.
One effective way to achieving this is to point out where your opponent said something that turned out not to be true – like a pledge to oppose tax hikes. If your opponent has done that, you can point out that the voter(s) was misled – so it wasn't their fault that they voted “wrong” in the past.
Another challenge is a natural tendency by some of your supporters who are less than enthusiastic – sometimes even paranoid – about welcoming into the campaign fold people who, in their opinion, weren’t smart enough to be with you from the get-go.
So your job between now and election day is two-fold:
A) Give people who have been with your opponent in the past a face-saving way to admit they made a mistake and, armed with new information, make the switch over to your camp.
B) Make sure everyone on your team rolls out the red carpet and warmly welcomes these “prodigal sons” home with the family. You don’t have to slaughter a calf, but make sure your campaign reinforces strongly your embrace of their return from the “Dark Side.”