Plaintiffs primarily rely on the "might have been presented" language of the rule, contending that since they could not present their Sherman Act claim in state court, res judicata cannot bar it. Defendant maintains on the other hand that this language expands, rather than contracts, the range of cases to which res judicata applies, and should include this case where plaintiffs raised a "claim, demand or cause of action" concerning the membership denial, and could have brought an antitrust count as an alternative ground to recovery either under state law or under federal law (with the other grounds pled as pendent state claims). The courts of Illinois have applied the "might have been presented" language in cases without relevance here, as, for instance, where a party was not permitted to intervene in a prior suit and hence could not present the issue upon which it later filed suit, see Inter-Insurance Exchange v. Truck Insurance Exchange, 88 Ill. App.3d 733, 44 Ill.Dec. 11, 12-13, 410 N.E.2d 1103, 1104-1105 (3d Dist. 1980). Slightly more relevant is the nineteenth century dictum that public policy does not allow a plaintiff to harass a defendant with multiple suits "when one suit in the proper court would have been all the litigation necessary." Lucas v. Compte, 42 Ill. 303, 305 (1866).
¶ 20 Plaintiffs correctly respond that, because the trial court denied their petition to intervene in defendants' marriage dissolution action, res judicata does not bar plaintiffs' claims here. Plaintiffs, having previously been denied intervention to present their claims asserted in this action, cannot now in fairness be barred on the ground that their claims could have been raised in the dissolution action. See Inter–Insurance Exchange of the Chicago Motor Club v. Truck Insurance Exchange, Inc., 88 Ill.App.3d 733, 736–37, 44 Ill.Dec. 11, 410 N.E.2d 1103 (1980); United Security Insurance Co. v. Hayman, 80 Ill.App.3d 309, 311, 35 Ill.Dec. 620, 399 N.E.2d 686 (1980); see also International Union, United Automobile, Aerospace & Agricultural Implement Workers of America, AFL–CIO, Local 283 v. Scofield, 382 U.S. 205, 86 S.Ct. 373, 15 L.Ed.2d 272 (1965) (if intervention is denied in a proceeding, the party so denied is not bound by the decision therein). Hence, res judicata does not apply to bar plaintiffs' claims in this action.