The O'Brien v. Brown case in 1972 was a significant U.S Supreme Court decision concerning the Democratic National Convention's delegate selection process. The respondents, who were California and Illinois delegates supporting Senator George McGovern for president, sought to prevent petitioners from seating rival delegations at the convention. They claimed that these rivals had been selected in violation of newly adopted party guidelines designed to ensure broad-based participation at grass-roots levels. However, the Supreme Court ruled against them by staying an injunction issued by a three-judge District Court panel which would have unseated certain Illinois and California delegates favoring other candidates over McGovern. The court held that it was inappropriate for federal courts to intervene in such political disputes due to their internal nature within political parties.

The dissenting opinion in O'Brien et al. v. Brown et al., 1972, argued that the Supreme Court should not have intervened in this case as it was a matter of internal party politics and not an issue of constitutional law or federal jurisdiction. The justices believed that the Democratic National Committee (DNC) had the right to set its own rules for delegate selection and seating at its national convention, even if those rules were controversial or disputed by some members of the party. They also felt that intervening would set a dangerous precedent for future cases where political parties might seek judicial intervention over internal disputes rather than resolving them through democratic processes within their organizations.