You should use UIViewAutoresizingFlexibleLeftMargin.
Here's why. You want your contents to move to the left, basically making it seem like the delete button is pushing the contents to the left, out of it's way. flexibleLeftMargin basically means your UILabel will stay fixed to the right side of your contentView. The reason you want this, is because the delete button actually causes your contentView to shrink it's width.
The autoresizingmask of your UILabel refers to how it behaves inside the contentView, not the cell.
Give it a try, it should work.
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