What’s up with those Campbell’s Soup ads?

For the past two Wednesdays, I’ve clipped full page Campbell’s Soup ads attacking Progresso soups for containing MSG (mono-sodium glutamate) and Datem (di-acetyl tartaric ester of monoglyceride) whereas the ads say Campbell’s Select Harvest soups only have “Real ingredients. Real taste.”  In February this year, Campbell’s announced it was cutting down on the salt, a good thing given that a can typically contains two full grams of sodium if you eat the whole thing, and many of the company’s soups still do.  The Select Harvest soups cut that down by half.    But why the attack on Progresso (owned by Betty Crocker/Pillsbury/Diagio)?  Brandweek says it’s about sales competition.  Maybe Progresso soups taste better?  Does anyone know the story on this?