Federal law sets limits on what individuals can donate to federal candidates, parties, and political action committees (PACs).
The case before the Supreme Court, as presented, would not touch limits on what individuals can give to candidates ($5,200 per election cycle), PACs ($5,000 per year), and national political parties ($32,400 per year).
It’s about a sort of “super limit” on contributions--what individuals can give across all federal committees. For the 2014 cycle, that’s $123,200, or more than twice what average American families make in a year. It's usually called the "aggregate contribution limit."
On October 8th, lawyers for Shaun McCutcheon will argue before the Supreme Court that this super limit should be thrown out.