On Sunday night, the enormous drugstore company CVS said it had agreed to buy the enormous health-insurance company Aetna for almost $70 billion. It’s a deal that, if government regulators and both companies’ shareholders give it their blessing, would be the biggest deal in the U.S. this year.

There are two main reasons CVS would benefit from acquiring a health insurer—one that’s specific to the economics of the health-care industry, and one that applies to just about any company that is trying to make money at brick-and-mortar stores in 2017.

First, if CVS does buy Aetna, it might be able to win over more business—both from individual consumers and from employers buying plans on behalf of their workers. In theory, that’s because CVS could gain a competitive edge by reducing the cost of providing care to Aetna’s customers.

How could it do this? CVS is not just drugstores. In 2006, it acquired a company called MinuteClinic, which operates walk-in clinics. CVS now has more than 1,000 of them, including in its stores and also in some Target locations. This is one of the main reasons CVS and Aetna could, together, save money: A company that sells insurance could start providing care directly, and steer customers not immediately to doctors but rather first to its own ensemble of nurses and pharmacists working at CVS locations.

An example illustrates why this could be powerful: If an Aetna customer has diabetes, it can be extremely costly (for both Aetna and the customer) for them to frequently see doctors for help managing their condition. Instead, a merged CVS-Aetna could encourage this customer to go to its walk-in clinics regularly for check-ins, potentially limiting those higher-cost doctor visits. A similarly salutary outcome could arise from having patients with other chronic conditions visit these clinics, perhaps to make sure they’re taking their medication—because when they aren’t, their conditions could worsen and they are likelier to need to see a doctor. In this way, CVS-Aetna could reduce the cost of the care it provides, perhaps prompting competitors to lower their prices in response.

The second reason CVS might see an advantage in buying Aetna is a single word that has appeared in a striking number of stories this year about any retailer that wants to keep making money: Amazon. Amazon is thought to be plotting a foray into pharmaceuticals—it reportedly has secured licenses that would allow it to sell, in 12 states, drugs, among other things. It could be the case that the company secured these licenses only to be able to sell medical devices, but analysts expect it has bigger ambitions—perhaps it will start up an online pharmacy that could ship medications. These reports have health-care companies like CVS bracing for the presence of a new, ruthless competitor that has record of completely changing entire industries. The proposed CVS-Aetna merger was not exactly unexpected—the two companies, after first partnering seven years ago, have been growing ever closer—but anticipation of Amazon’s next moves could have hastened things.

From this vantage, CVS’s pursuit of a deal is of a piece with all the other unusual things stores are doing to defend themselves from online shopping, such as installing juice bars and spas. “They’re trying to figure out how to utilize their footprint better, and by merging with an insurer, their hope clearly must be to be driving more foot traffic into their facilities and figure out a way how to be more on the front line of health-care delivery,” says Leemore Dafny, a professor of business administration at Harvard Business School.

Of course, there might be still another reason for the deal, Dafny noted. “There’s a question as to whether these two companies couldn’t figure out ways to get [the same] benefits without merging,” she told me. “Obviously, Wall Street loves mergers.” Indeed, the financial firms arranging the deal stand to earn in the neighborhood of $130 million if it goes through.

And if it does, will it save consumers money or give them better care? Because the proposed merger is between such large companies, that’s a little hard to predict. In general, consolidation in the health-care industry has primarily benefited the companies making the deals. That said, two experts I talked to said that this one could be different. Dafny said she sees more risk for CVS’s shareholders—the company could turn out to overpay for the acquisition—than for consumers. Atul Gupta, a professor at Wharton, agreed: “In the short term it will probably benefit existing CVS/Aetna customers if they start providing some innovative new services or pass through cost benefits to them,” he wrote to me in an email.

Others—granted, people who are skeptical of mergers more generally—are skeptical of this one too. Brian Feldman, of the antitrust research group Open Markets Institute, argues that mergers in the past few decades have “created a funhouse mirror situation—the drug industry’s incentives have become incredibly warped.” The market for drugs is shaped by five different types of companies: drug manufacturers, wholesalers, pharmacies, insurers, and pharmacy benefit managers (which function as middlemen between manufacturers and insurers). If the CVS-Aetna deal goes through, Feldman argues, CVS would have a foothold in every category but manufacturing, meaning that it would encounter competition from other companies less often.

As government regulators weigh whether to greenlight the CVS-Aetna deal, it’s points like these that they will mull on. One clause I included at the top of this piece—“if government regulators and both companies’ shareholders give it their blessing”—may have read as a formality, but, more so than in the past, there’s a real question of whether the Department of Justice will approve of a merged CVS-Aetna.

Broadly speaking, there are two types of mergers: horizontal and vertical. A horizontal merger is between rivals, and is the type that tends to make regulators worried that companies benefit, via decreased competition, at the expense of consumers. A vertical merger is between companies that do different things in the same industry. The case that these mergers hurt consumers is not always as straightforward. Consider this example: If one company that makes T-shirts bought the rest (a horizontal merger), it could dictate the price of T-shirts. But if a department store bought one T-shirt maker (a vertical merger), it wouldn’t have so much sway over the market.

Antitrust regulators have tended to be more permissive of deals like the latter than deals like the former. Lately, though, the DOJ’s stance on vertical mergers—which is what the CVS-Aetna deal represents—appears to have changed, as my colleague Derek Thompson has written. In 2011, the Obama administration approved of a merger between NBCUniversal (a media company) and Comcast (a media-distribution company). But last month, the DOJ said it would sue to block a very similar deal, between Time Warner (a media company) and AT&T (a media-distribution company).

That seemed unusual under an administration that is outspokenly opposed to government regulation. What changed? Makan Delrahim, DOJ’s head of antitrust, explained his thinking in a speech last month. In the case of the Comcast-NBCUniversal merger, the government gave a thumbs-up, but only a conditional one: Regulators have been keeping close tabs on the company to make sure it hasn’t been engaging in any anticompetitive tactics. Delrahim said this isn’t how it should be: If a merged company is potentially anticompetitive, it just shouldn’t be approved in the first place, so the government doesn’t have to keep watch.

CVS, Aetna, and their shareholders—as well as those bankers who engineered the merger—will be eager to know if Delrahim feels the same about this deal. Another company will too: If CVS’s deal goes unchallenged, AT&T will probably want a good reason why its vertical merger did not.