How did McCutcheon v. Federal Election Commission change the earlier ruling in Buckley v. Valeo?

In McCutcheon v. Federal Election Commission (2014), the U.S. Supreme Court struck down the aggregate contribution limits established by the Federal Election Campaign Act (FECA), which had been previously upheld in Buckley v. Valeo (1976).12

In the 1976 Buckley ruling, the Court had characterized aggregate limits as a "quite modest restraint upon protected political activity" and a "corollary" to the base contribution limits, finding them justified by the government's interest in preventing corruption or the appearance of corruption.1

However, in McCutcheon, the Court departed from this earlier precedent by invalidating those same aggregate limits. The Court concluded that these limits were not necessary to prevent the circumvention of base contribution limits, noting that other existing regulations already made it difficult to funnel large sums to candidates indirectly. By striking down these aggregate caps on the total amount an individual could contribute to multiple federal candidates, party committees, and noncandidate political action committees (PACs), the McCutcheon decision significantly altered the campaign finance landscape that had been defined by Buckley for over three decades.123