As Inc. (AMZN) wraps up its record-breaking Prime Day, estimated by the Street to have raked in nearly $3 billion in sales on July 11, one bear says the ecommerce giant could be in for a rude awakening as it faces threats from Washington, arising in part from a particularly rocky relationship with the Trump administration. (See also: How Amazon Rakes in Big Bucks From Prime Day.)

Hedge fund manager Douglas Kass of Seabreeze Partners Management Inc. says early discussions and due diligence are being considered in the legislative chambers in Washington regarding possible antitrust opposition to Amazon’s business practices, pricing and expansion.

As a result, the investor says he is shorting AMZN, indicating that if he is correct, “word of this could lower Amazon’s shares by 10% overnight.” Regarding the chatter on Capitol Hill, Kass says, “this has the potential of being the biggest business news story of the year.” The hedge fund manager is known for his short positions on Marvel Entertainment just a year and a half before it went bankrupt in the '90s, along with betting against the big banks into the U.S. financial crisis of 2007.

Whole Foods' Impact

Also this week, Reuters reported that the top Democrat on the U.S. House of Representatives’ antitrust subcommittee has voiced concerns about the Seattle-based online retailer's $13.7 billion acquisition of organic food grocer Whole Foods Market Inc. (WFM), and is pushing for a hearing to look into the deal’s potential impact on consumers.

On Thursday, Rep. David Cicilline requested the hearing in a letter to the chair of the House Judiciary Committee, indicating that “Amazon’s proposed purchase of Whole Foods could impact neighborhood grocery stores and hardworking consumers across America.” (See also: Amazon: 'Compounding Love of Prime Continues,' Says Street Bulls.)

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