How has the federal government tried to limit campaign spending?
The bipartisan campaign Reform act of 2002, better known as the McCain - Feingold Act regulates the financing of political campaigns in the United States. It limited the major political parties fundraising and spending efforts in regard to political advertising.
The act has been gutted since then. The supreme court held that some aspects of the law are unconstitutional and other groups have utilized loopholes to avoid the letter of the law and still raise and spend vast sums on political adds.