Rite Aid stock fell as much as 18.5% in morning trading after a Bloomberg report that the FTC is "worried" about the details of Walgreens planned buyout of its smaller rival. It's since pared about half of those losses.

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Data: Money.net; Chart: Andrew Witherspoon / Axios

Walgreens had planned to sell hundreds of its stores to regional pharmacy chain Fred's, but reports are that the FTC may not see these divestitures as bold enough to avoid antitrust concerns.

Why it matters: The Obama Administration ramped up antitrust oversight and one of the big question marks of the Trump Administration is whether it will get tough on mergers or take a more traditional Republican stance. The Walgreens-Rite Aid merger could be an important clue in this puzzle.