[dragonwriter]

> Wouldn't an antitrust claim against Apple likely fail if the plaintiff cannot establish they actually have market power in the smartphone market?

Well, assuming it is one based on abuse of market power and not the other kinds of antitrust violations (e.g., combination in restraint of trade, etc.), it would fail if the plaintiff couldn't establish that Apple had market power in the market for the product for which they allegedly abused market power. If that was iPhones, for instance, that would be the market for iPhones plus whatever products empirically people substitute for iPhones in response to pricing changes. (Of course, if Apple has market power, there is some range in which the “plus...” part is “none”, since market or pricing power is the ability to raise prices without driving sales to a competing good.)