I haven’t seen any evidence of that....
I don’t know how you managed to miss that Costco is left wing, I have been boycotting them since the mid 90s.
http://www.slate.com/id/2104988/
So far this campaign cycle, Costco CEO James Sinegal has made campaign donations of $93,500 according to OpenSecrets.org—all of it to Democratic candidates and entities. Brotman has donated $38,250 in this cycle, again all to Democrats. In addition, Brotman and Sinegal have also given $95,000 apiece to the Joint Victory Campaign, one of the most influential of the anti-Bush527 committees, independent entities that can accept unlimited donations from individuals. Sol Price, the founder of Price Club, which merged with Costco in 1993, has given more than $44,000 to Democratic campaign causes this cycle.
Wal-Mart, by contrast, focuses its fundraising largely on Republicans. Jay Allen, Wal-Mart’s senior vice president for corporate affairs, is a Bush Pioneer, meaning he’s raised at least $100,000. Wal-Mart CEO Leo Scott has donated to the president’s re-election campaign. Through July 6, according to Sheila Krumholz, research director at the Center for Responsive Politics, Wal-Mart—the company, its PAC, and individuals employed by it—have made political donations of $1.658 million. Of that, $1.34 million, or 81 percent, went to Republicans. While many corporate PACs hedge their bets and give to both parties in rough proportion to their control of Congress, “Wal-Mart stores appears to be a more ideologically aligned company,” said Krumholz.