Further activism thumb|McCarthy in 1968 McCarthy opposed Watergate-era campaign finance laws, becoming a plaintiff in the landmark case Buckley v. Valeo, 424 U.S. 1 (1976), in which the U.S. Supreme Court held that certain provisions of federal campaign finance laws were unconstitutional. McCarthy, the New York Civil Liberties Union, philanthropist Stewart Mott, the Conservative Party of New York State, the Mississippi Republican Party, and the Libertarian Party were the plaintiffs in Buckley, becoming key players in killing campaign spending limits and public financing of political campaigns.
Further activism thumb|McCarthy in 1968 McCarthy opposed Watergate-era campaign finance laws becoming a plaintiff in the landmark case Buckley v. Valeo, 424 U.S. 1 (1976), in which the U.S. Supreme Court held that certain provisions of federal campaign finance laws were unconstitutional. McCarthy, the New York Civil Liberties Union, philanthropist Stewart Mott, the Conservative Party of New York State, the Mississippi Republican Party, and the Libertarian Party were the plaintiffs in Buckley, becoming key players in killing campaign spending limits and public financing of political campaigns.