Tracking the flow and impact of money in politics has long been one of Mother Jones' main beats. Since the 2010 Citizens United decision paved the way for a new era of bottomless election spending, we've been focused on what we call "dark money"—the hundreds of millions of dollars being dropped by outside groups, much of it without full disclosure of where it's coming from.

The key players in this new world are super-PACs, which may raise and spend unlimited sums of money for or against candidates; and 501(c) nonprofit groups, which may make political ads and give money to super-PACs without disclosing their donors.

We wanted to visualize the major super-PACs and 501(c)s in a way that would provide both a good overview of outside spending in this election cycle as well as detailed information about each group. The universe metaphor was in keeping with the idea of dark money, and provided an eye-catching way to show how groups share orbits (i.e., super-PACs linked directly to nonprofits) and constellations of similar organizations (e.g., labor unions and pro-business groups). And just as in outer space, not everything is visible to the naked eye, as signaled by the fuzzy edges on the 501(c) groups.

The current version of this chart shows just one slice of the dark-money universe: There are hundreds of smaller super-PACs and 501(c)s that are not included in this version. Over the months leading up to Election Day, we'd like to expand this universe to include more groups. We'd also like to include links to profiles of groups and their top donors, present more information on which candidates each group is spending for and against, and add an animated timeline showing super-PACs' growth over time.