During his campaign for president, Donald Trump claimed Amazon was a monopoly he would go after for anti-trust violations if elected. Sure, Trump didn't like the coverage he was receiving in the Washington Post, which Amazon CEO Jeff Bezos owns. But even just judging by the latest holiday sales numbers, Amazon so decisively dominates online shopping that other retail giants can barely compete. If Trump decided to make good on his promise, should Bezos be worried?

Amazon’s dominance is just that: a company outdoing the competition in capitalism’s grand tradition.

If success alone were against the law, then yes. Online sales covering these five days amounted to nearly $13 billion. That’s 15 percent more than the same period one year ago, according to Adobe Digital Insights. On Black Friday, online shoppers using mobile devices spent more than $1 billion in a day—a first. Meanwhile, the share of retail dollars spent online is growing at the fastest rate ever. Since by some estimates Amazon accounts for half of all online shopping, all these trends certainly mean nothing but good things for Bezos' balance sheet—both now and for the foreseeable future.

"Once again, Amazon is best positioned to take advantage of the shifts," says Jason Goldberg, vice president of commerce and content at digital agency Razorfish.

The question is whether that advantage becomes too much of an advantage—if Amazon's success tilts into something more nefarious that blocks healthy competition. So far, experts say Amazon's dominance is just that: a company outdoing the competition in capitalism's grand tradition. But it may be on the verge of becoming the kind of monopoly that Trump's top techie, Peter Thiel, says all companies should strive to be: "the kind of company that is so good at what it does that no other firm can offer a close substitute."

Staying Ahead

No other retailer looks close to becoming an Amazon substitute yet. A few intrepid retailers, including Walmart and Target, are certainly trying to compete, but they're still so far behind. Amazon scored $79 billion in online sales last year. Walmart came in a far-distant second at $13.5 billion. That’s not a gap; it’s a chasm.

Amazon's advantage would seem to come from doing just what Thiel describes: seizing its market opportunity first (it started selling books online in 1995) and doing online shopping better. Thanks to its first-mover advantage and some serious foresight, the company has already built a vast network of fulfillment centers that span the globe. It hires and knows how to deploy hundreds of thousands of seasonal workers. It simply enjoys a logistical superiority that it's extending into its own trucks, cargo planes, and drones. On the front end, it’s even opening bookstores and grocery stores that can double as distribution centers in their own right while venturing into the last remaining territory its key competitors still dominate: offline shopping.

“Amazon now has the scale where it can offer fulfillment options that are very difficult to match by others,” says eMarketer analyst Yoram Wurmser. “This is an enormous problem for big box retailers.”

Another problem would-be Amazon rivals face stems from shoppers' increasing preference to browse for products on their phones. Despite this predilection, browsers still become buyers less than half the time on smartphones as they do on desktop computers. Once again, however, Amazon is the exception, or at least the farthest ahead.

“Amazon has far less of a mobile gap than any other retailer—largely driven by the fact that 240 million shoppers have stored their payment information and shipping information on Amazon already,” says Goldberg.

Fair Trade

Despite its success, however, Amazon may escape the evil eye of antitrust regulators for the simple reason that offline shopping still overwhelmingly dominates retail. Legal experts say it's doubtful online retail would even constitute a separate anti-trust market. "Nearly 90 percent of Christmas sales will be through brick and mortar stores rather than online," says Paul Denis, a partner at the firm Dechert LLP who specializes in antitrust law. "It looks like brick-and-mortar is not dead yet."

For the moment, Denis says regulators also apply different antitrust analyses to online sales depending on the sector. The Federal Trade Commission, for example, ignores online competition when evaluating supermarket and dollar store mergers, Denis says, but took account of online competition for individual and small business customers when it came to blocking the merger of Office Depot and Staples in May.

Even if online retail did consitute its own antitrust market, commanding great market share by itself does not mean a company is in violation of antitrust laws. "Fifty percent is not a monopoly," says Ben Gomes-Casseres, a professor at Brandeis International Business School who studies business alliances. "It's a strong market position, yes. But what matters is how you behave when you're big."

And so far, Amazon is still playing nice enough. Yes, Amazon has thrown its weight around. It banned Apple TV and Chromecast from its online store. It uses the data it gathers from running its store to sell its own branded products, from electronics to clothes. But neither of those moves violate antitrust laws, says Gomes-Casseres. After all, Apple TV and Chromecast are still widely available in other markets, and it's not like this is the first time a big retailer has pushed its own product lines.

"As a legal matter in the US, being a monopolist requires high market share and the power to exclude others from the market," Denis says. But Amazon's business actually depends on including other sellers: its third-party marketplace, which allows others to sell stuff on its site, makes up a huge part of Amazon's business.

Ultimately the onus is on competitors to stay pace with the retailer that has so changed the game for online shopping, Gomes-Casseres says. "The challenge is more for brick-and-mortar companies to compete with this," he says. It's not exactly that Amazon has a monopoly; it's that its retail rivals haven't innovated fast enough. And as Amazon well knows, getting to the kind of influence it now enjoys can take quite a while.