In antitrust case, plaintiffs proposed four theories: First, that Comcast’s clustering made it profitable to withhold local sports programming from its competitors, resulting in decreased market penetration. Second, that Comcast’s activities reduced the level of competition from “over builders”. Third, that Comcast reducedthe level of “benchmark” competition on which customers rely to compare prices. And fourth, that clustering increased Comcast’s bargaining power relative to content providers. The District Court accepted the over-builder theory of antitrust impact as susceptible to classwide proof, and rejected the other three. After certification was affirmed, Comcast sought review on the question of whether a district court can certify a class action without resolving “merits arguments” that bear on the Rule 23(a) pre-requisites and the predominance inquiry under Rule 23(b)(3). The Court granted review of a different question: “Whether a district court may certify a class action without resolving whether the plaintiff class has introduced admissible evidence, including expert testimony, to show that the case is susceptible to awarding damages on a class-wide basis.” The majority, reversing certification, concluded as follows: “If respondents prevail on their claims, they would beentitled only to damages resulting from reduced overbuilder competition, sincethat is the only theory of antitrust impact accepted for class-action treatment by the District Court. It follows that a model purporting to serve as evidence of damages in this class action must measure only those damages attributable to that theory. Calculations need not be exact, but at the class-certification stage (as at trial), any model supporting a plaintiff’s damages case must be consistent with its liability case, particularly with respect to the alleged anticompetitive effect of the violation.” Comcast Corp. v. Behrend, 133 S. Ct. 1426 (2013).