Factbox: Recent U.S. Supreme Court campaign finance decisions

(Reuters) - The U.S. Supreme Court on Wednesday struck down a key pillar of campaign finance law by allowing wealthy donors to give money to as many political candidates, parties and committees as they wish. The decision on McCutcheon v Federal Election Commission was just the latest in a string of recent 5-4 cases that have loosened regulations on political contribution laws. Here are some other major cases. CITIZENS UNITED V FEDERAL ELECTION COMMISSION (2010) This ruling is seen as heralding the dawn of a new era of major money being injected into campaigns, particularly with the subsequent rise of so-called Super PACs - groups that can take unlimited donations but cannot contribute directly to campaigns. The controversial 5-to-4 decision, which is still denounced by many liberals, found that the government may not limit corporate and labor union spending on elections and was seen as favoring Republicans. Despite Democratic opposition to the new big-money landscape, many in the party - including President Barack Obama - have subtly embraced the changes, benefiting from Super PACs themselves. BUCKLEY V VALEO (1976) Considered the country's seminal campaign finance ruling, the Supreme Court in Buckley v Valeo upheld many of the limits imposed by the 1974 Federal Election Campaign Act. But it struck down limits on spending by individual candidates. FEDERAL ELECTION COMMISSION V WISCONSIN RIGHT TO LIFE (2007) In this 5-to-4 decision, the Court ruled against the constitutionality of part of a controversial provision of the Bipartisan Campaign Reform Act of 2002, which is commonly known as McCain-Feingold. The provision had banned the use of corporate funds for political ads in the 60 days before an election: Chief Justice John Roberts wrote the majority opinion, ruling against the ban when the ads were not specifically for or against any candidate. DAVIS V FEDERAL ELECTION COMMISSION (2008) This decision also stemmed from McCain-Feingold. Justice Samuel Alito's majority opinion ruled that the imposition of higher contribution limits for candidates running against self-funded opponents violated the First Amendment. Before the decision, candidates who could afford to self-fund their campaigns faced tighter restrictions than their rivals. ARIZONA FREE ENTERPRISE CLUB'S FREEDOM CLUB PAC V BENNETT (2011) Roberts also wrote this decision, which struck down an Arizona law that provided additional public money to political candidates for state office who face big-spending opponents, ruling it violated free-speech rights. National attention to public election funding has receded in recent years, as both Obama and his 2012 presidential election campaign opponent, Republican Mitt Romney, turned down federal campaign funds. (Reporting by Gabriel Debenedetti; Editing by Dan Grebler)