Most political giving is straightforward: You find a candidate or cause you support — or respond to a solicitation — and send the money straight to the campaign, political action committee, or party.

But that goes to one person at a time. If you want to support multiple candidates, you’d have to look them all up and write multiple checks to them. If the state party organized a big fundraiser with numerous campaigns, you’d still have to write a check to each one.

Joint-fundraising committees bring multiple campaigns and parties together, allowing donors to write one check to the group and have it automatically divided. The maximum amount you can give by law to a joint-fundraising committee is simply the total of the maximum amounts you can give to each individual recipient. Right now, individuals can give up to $2,700 to a federal candidate per election. If a joint-fundraising committee has 10 candidates, each donor can give it $27,000. And so on.

Here’s a real example: If you want Democrats to take control of the U.S. House of Representatives this November, you can donate to House Victory Project and have their money sent to 31 different congressional candidates.

On the other hand, if you want to help Republicans maintain control of the U.S. House of Representatives this November, you can make one donation to Protect The House. They’ll split it for you among 43 recipients.

Notice how money collected by Protect the House goes to state Republican parties, including the Pennsylvania and New Jersey GOP? That’s because joint-fundraising committees aren’t limited to sending funds to candidates. State parties can get in on the action, too, and that’s where the big money comes in — the law allows donors to give more to parties than individual candidates.

Want to support the Democratic Party as a whole, not individual candidates? Democratic Grassroots Victory Fund will divide your check among 52 recipients: the party in each of the 50 states, plus Washington, D.C. and the national party. That allows for six-figure donations, and some donors have given $849,000 at once. Because campaign contributions are limited by year, a two-year campaign season means donors can double their contribution. One donor has given nearly $1.7 million this election season; two others have given about $1.6 million each.

It wasn’t always this way. These massive checks are only possible because of a recent change to campaign finance limits. There used to be a cap on the total amount donors could give, so they couldn’t just max out to as many candidates as they wanted. The U.S. Supreme Court struck down aggregate limits in McCutcheon v. FEC in 2014, paving the way for larger joint fundraising committees than ever before. At the time, individual donors couldn’t give more than $123,000 in a single two-year cycle.

The result has been a boom in joint-fundraising committees, both in the number of them and the amounts they’re raising. While they’ve existed for decades, these committees have grown larger than ever in recent years, and candidates have received more and more money through them.