If only Wal-Mart had better branding...
The only way that has a chance of working is if they never let this brand touch one of their stores or their logo. Otherwise the association will wash away any kind of cachet the brand originally had.
the perception here seems to be that Wal Mart only sells stuff that 'people of Wal Mart' want to buy
there's is probably plenty of room in Wal Marts brand to get at - 'we sell everything, down market stuff and up market stuff'
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wal mart's impact on Main Street - while (somewhat) real - is a separate question