How could disclosure requirements address campaign-finance corruption according to the McCutcheon majority?

In the plurality opinion for McCutcheon v. Federal Election Commission (2014), the U.S. Supreme Court majority argued that broad disclosure requirements serve as a legitimate and effective alternative to aggregate contribution limits for addressing campaign-finance concerns.1

According to the Court, such requirements help deter actual corruption and avoid the appearance of corruption by exposing large political contributions and expenditures to the "light of publicity". By ensuring transparency, these measures allow the public to see whether elected officials are potentially influenced by moneyed interests, thereby promoting accountability without imposing the "significant First Amendment costs" associated with aggregate limits on how many candidates or causes a donor may support.1

The Court emphasized that while the government has a compelling interest in preventing quid pro quo corruption—the direct exchange of an official act for money—it must pursue this interest through means that do not unnecessarily abridge protected First Amendment activities. Disclosure is viewed as a less restrictive, yet powerful, tool to maintain the integrity of the electoral process.1