The move is unusually early for a retailer — happening weeks before the official holiday season kickoff over the Thanksgiving weekend — and could squeeze Target's profit margins. [...] the strategy underscores how retailers are willing to do whatever it takes to grab shoppers in the critical holiday shopping season, which accounts for about 20 percent of the retail industry's total sales The incentive comes four months after Target unveiled a permanent free shipping offer for those spending at least $50 online, a strategy the company said has had strong reception. The free shipping holiday incentive is one of a number of enticements that Target is pushing, from more trendy merchandise to spiffed up apps, to win back consumers turned off by its own problems as well as industrywide challenges. Target also aims to play catch up with rivals who've been offering services that cater to shoppers who want to jump back and forth from stores to their smartphone.