Buckley considered the constitutionality of a federal campaign financing law that imposed numerous restrictions on both candidate's own spending and the contributions of individuals to campaigns.  The challenge to the act was brought by unlikely political bedfellows, including conservative Senator James Buckley and liberal anti-war candidate Eugene McCarthy. 

The Court in Buckley upheld some of the provisions of the act, while striking down others.  In particular, the Court invalidated limits placed on the personal expenditures of candidates for federal office, thus paving the way for runs by wealthy candidates such as Ross Perot in 1992.  The Court also struck down a $1000 limit on individual spending on behalf of a campaign, concluding that the restriction was not closely tailored to serving the government's asserted interest in preventing corruption. On the other hand, the Court upheld limits on individual contributions to campaigns and the use of federal matching funds for candidates who agree to abide by federal spending limits.  The Court also upheld donor disclosure requirements, except as they apply to controversial third parties where disclosure might prove embarrassing to donors.

Citizens Against Rent Control (1981) considered the legality of a Berkeley, California ordinance limiting contributions to campaigns to support or oppose ballot measures to $250.  The Court invalidated the limitation, concluding that the concern in Buckley about "buying influence" had little applicability in the case of ballot measures.  In reaching its conclusion, the Court seemed either to be applying strict scrutiny--or something very close to it.

In 2007, the Court signalled a new willingness to strike down campaign finance regulations.  In Federal Election Commission v Wisconsin Right to Life, the Court voted 5 to 4 to invalidate a key section of the McCain-Feingold Act that banned corporations and unions from buying broadcast ads that mention the names of candidates for federal office in the weeks immediately before an election.

In 2010, the Supreme Court considered whether the First Amendment allowed the government to impose limits on direct funding of political attacks by a corporation.  Citizens United v Federal Election Commission involved a challenge to a corporately-funded documentary attacking the candidacy of Hillary Clinton.  Voting 5 to 4, the Court ruled that the First Amendment prohibited the government from banning political spending by corportations (and, presumably, labor unions) in candidate elections.  Writing for the Court, Justice Kennedy wrote “If the First Amendment has any force, it prohibits Congress from fining or jailing citizens, or associations of citizens, for simply engaging in political speech.” The decision overruled earlier Court decisions (Austin, and portions of McConnell)  that suggested limitations on corporate speech in campaigns serve the compelling interest of in eliminating the distorting effects on a campaign of immense aggregations of wealth.  The Court also rejected the argument that the law served the compelling goal of reducing political corruption. Justice Stevens, in dissent, called the majority decision "a rejection of the common sense of the American people."  The Court  affirmed F.E.C. rules requiring disclosure of the name of the sponsor of the political message.  The case did not consider the constitutionality of the limitation on corporate donations directly to the campaign of a candidate for federal office.  The Citizens United decision was attacked by President Obama in his 2010 State of the Union Speech, and Democrats in Congress proposed new regulation to limit the effect of a ruling that they believe clearly favors Republicans, who are likely to receive disproportional corporate support in election campaigns.