The Citizens United v. Federal Election Commission case stands as a monumental milestone in the history of campaign finance in the United States. Debated in 2009 and decided in 2010, this case posed a direct challenge to the provisions of the Bipartisan Campaign Reform Act (BCRA) of 2002, also known as the McCain-Feingold Act, which had been the bedrock of campaign financing regulations.

Citizens United, a conservative nonprofit organization, sought to air a film critical of Hillary Clinton, who was then a candidate for the Democratic presidential nomination, in the run-up to the 2008 elections. However, under the BCRA, specific provisions, such as the prohibition on corporations and unions from funding "electioneering communications" within 30 days of a primary or 60 days of a general election, were challenged in the case.

In a 5-4 decision, the Supreme Court ruled in favor of Citizens United. Justice Anthony Kennedy's majority opinion held that political spending is a form of protected speech under the First Amendment. The decision concluded that restrictions on independent political expenditures by corporations and unions violated their right to free speech.

The ruling effectively removed certain limits on corporate and union spending in elections, allowing them to spend unlimited amounts on independent expenditures, such as advertisements supporting or opposing political candidates. This led to the rise of Super PACs (political action committees), which are independent expenditure-only committees that can raise and spend unlimited sums of money on behalf of candidates as long as they do not directly coordinate with the candidate's campaign. Super PACs have significantly increased the amount of money in politics and have been a major source of controversy since the Citizens United decision.

The ruling has sparked intense debate, with critics arguing that it has deepened the influence of money in politics. They contend that it has given the wealthy, corporations, and special interest groups an unfair advantage in the electoral process, potentially drowning out the voices of ordinary citizens and undermining the principles of fair and equal representation.

There have been widespread calls for campaign finance reform to address concerns about the influence of money in politics. Various proposals, including a constitutional amendment to overturn the decision, legislation aimed at increasing transparency in political spending, and the introduction of public financing of campaigns, have been put forth.

Citizens United v. Federal Election Commission remains a polarizing and pivotal case in campaign finance. Its implications continue to shape the political landscape, prompting ongoing discussions about the balance between free speech rights and the regulation of money in the electoral process.