Back in October, we wrote an explainer on McCutcheon v. FEC, the case of aggregate donor giving on which the Supreme Court ruled today. We're reposting it here. And you can read the full McCutcheon ruling here.

So what's this case all about?

Shaun McCutcheon is a conservative businessman from Alabama who likes to give money to political candidates and committees. He dished out thousands of dollars in donations last election cycle. He says he would have given more, if not for the law that says an individual can only donate a certain total amount each cycle to candidates and certain political committees. McCutcheon thinks the law is a violation of the First Amendment. The Republican National Committee, which joined McCutcheon in the case, agrees. From the perspective of the Federal Election Commission and those who favor tighter campaign finance restrictions, the limits are necessary to fight corruption.

How much can individuals give under the current law?

For the 2013-2014 cycle, individuals can give a total of $123,200 to candidates, national party committees and certain political committees, including a $48,600 limit on what individuals can give to candidates. There are also other limits. For example, an individual can only give $2,600 to a specific candidate for federal office, per election per cycle. While this case is focused on the aggregate limits, it's important keep all the limits in mind. (More on that in a moment.)

Why do these limits exist, anyway?

Because of changes to the Federal Election Campaign Act in 1974 that instituted them and created the FEC, the body that oversees and enforces campaign finance regulations. The act was amended in the wake of violations in the Watergate scandal.

So if the aggregate limits are struck down, what will it mean?

A couple of things. For one thing, wealthy donors who can afford to make many donations will have greater influence when it comes to donating to candidates directly. Under the current aggregate limit of $48,600, an individual can max out at 18 federal candidates per cycle. Think of how much more they could give in total if they maxed out at 50 candidates -- or even more.

Secondly, as The Washington Post's Robert Barnes and Matea Gold explain, defenders of the limits worry that such a ruling could dramatically increase the power and size of joint fundraising committees, which harness the fundraising power of different political committees. For example, the Obama Victory Fund joined together the DNC and Obama campaign last election cycle.

In addition, those who favor limits also worry that such a ruling could lead to doing away with all limits, including the individual limits mentioned above. It's worth noting that in the current environment, there are already entities called super PACs that are not subject to limits on how much money they can accept from donors.

So what is the court going to decide?

It's not clear. But it looks like Chief Justice John Roberts and Justice Samuel A. Alito Jr. will be key in this case. It's less clear where they will come down, compared to the other conservatives justices, write Barnes and Gold.

Thanks for the explanation. Do you have something I can send my friends that doesn't take as long to go through?

Yes! Just watch this video.