I'm officially retracting my support for bernie sanders
Why did you originally choose to vote for Sanders?
I voted for him as the only option with respect to voting rights. I don't think he's the right choice anymore.
It sounds like you changed your political views over time. It's fine to change your mind and decide to vote for someone else in the future.
I think he may have lost his way due to criticism from the media.
Could be. For whatever reason, you are free to support anyone you want. You are equally free to withdraw that support when you deem it appropriate.