Final answer:
The most common argument for regulating campaign donations is to prevent wealthy individuals from having excessive influence on elections, as this can lead to a system where money, rather than the democratic process, determines political outcomes.
Step-by-step explanation:
The most common argument for regulating campaign donations is that unregulated giving allows wealthy people to "buy" elections. This concern is rooted in the idea that when individuals can contribute large sums of money to numerous candidates, they may exert an excessive amount of influence on the political process, potentially diluting the influence of less wealthy individuals. The Supreme Court's decision in Buckley v. Valeo recognized the need to protect the democratic process by upholding limits on the amount that individuals can give to candidates. Moreover, the Bipartisan Campaign Reform Act of 2002 attempted to address the issue of "soft money" by placing limits, highlighting the ongoing effort to balance the concerns of free speech with the prevention of corruption.