ActBlue makes it very easy to set up a form that takes a single donation and splits it among many candidates, you can even include other groups and organizations.
Here’s their guide to creating a list to donate to. It’s easy to sign up, only takes about 15 minutes, and once you created and saved a list, you can share it with other people too.
These kinds of lists are great because they’re efficient. When you donate it just charges you once, there’s only one transaction fee on the backend, and all the candidates split the money. Or you can punch in specific amounts for each person you’re giving to. There’s the option to make it a recurring monthly donation, which is great, and you can either share your email with the campaigns or opt out.
The only downside is that ActBlue only allows donations to liberal candidates, so if you want to include conservative candidates as well, you’ll have to give separately to them. There is another site https://winred.com/ which is focused on small dollar fundraising for conservative candidates. They allow similar forms to be made to raise money for a group of candidates, the setup process takes a little bit longer, but it’s a viable alternative.