Final answer:
Buckley v. Valeo struck down the element of the Federal Election Campaign Act that imposed limits on campaign spending by candidates and their campaigns, determining it violated First Amendment rights.
Step-by-step explanation:
The Supreme Court case Buckley v. Valeo struck down the element of the 1971 Federal Election Campaign Act that set limits on the total amount candidates for federal elective office could spend on their campaigns. The Court ruled that these limits violated the First Amendment rights of individuals to engage in free speech, which includes spending money to influence elections. While the case upheld restrictions on campaign contributions, it overturned restrictions on expenditures by candidates and their families, as well as the campaigns' total expenditures.