Django Taggit - Tag Associations not Saving from Custom Admin Form

Question

Going nuts over here... From within the shell, I can do:

product.tags.add("a_new_tag")

The tag is added to the db, and the tag association with the product works correctly. (i.e., when I do Product.objects.filter(tags__name__in=["a_new_tag"] the appropriate product spits out)

What I need to do is add some tags in the admin when the form is processed.

Here is my form code (read the comments in lines 4 and 5):

class ProductForm(ModelForm):
        def save(self, commit=True):
            product = super(ProductForm, self).save(commit=False)
            product.type="New Type to Confirm Info is being Saved Correctly" //this is saved to the product.
            product.tags.add('a_new_tag_1') //the tag is saved to the taggit db, but the association with the product isn't kept.
            product.save()
            self.save_m2m()
            return m

I tried to do the saving in the admin class instead, but this doesn't work either:

class ProductAdmin(admin.ModelAdmin):
    form = ProductForm
    def save_model(self, request, obj, form, change):
        obj.type="new_type" //this works 
        obj.tags.add("a_new_tag_2") //tag association not saved
        obj.save()
        form.save_m2m()

What am I doing wrong? Thanks in advance!