Today marks six years since the Supreme Court ruled on Citizens United v. FEC. Since then, Citizens United has become shorthand for the problems with the state of campaign finance in the U.S.: unlimited corporate spending, lack of disclosure and the outsized influence of a small number of wealthy individuals. And all these things are shaping up to be more important than ever in the 2016 elections.

The case centered on a film that the conservative advocacy group Citizens United had made about Hillary Clinton. During the 2008 election, the group wanted to run and advertise the film on TV, but a lower court had ruled that they were prohibited from doing so because they were a nonprofit corporation and the film mentions a candidate, thus making it an “electioneering communication.” In Citizens United v. FEC, the Supreme Court ruled in a 5-4 vote that the ban on political spending by corporations and unions was unconstitutional because it violated the First Amendment’s protection of free speech. As long as this spending was not coordinated with campaigns, the court said, it would not “give rise to corruption or the appearance of corruption.”

So, Citizens United allowed corporations to spend on elections. But it isn’t the whole story of how we got to where we are today. Another very important decision followed Citizens United two months later: Speechnow.org v. FEC. This is the case that led to super PACs as we now know them, striking down limits on contributions to groups that only make independent expenditures, but upholding the requirement that they disclose donors. The court found that the government has “no anti-corruption interest in limiting contributions to an independent expenditure group.”

This ruling, combined with the corporate spending allowed by Citizens United, created super PACs: groups that can accept unlimited donations — from individuals or corporations — and spend as much as they want on expressly advocating for candidates, as long as they don’t coordinate with those candidates. This was unprecedented: While 527 and 501(c)(4) groups had been able to spend unlimited amounts, they were prohibited from explicitly advocating for the election or defeat of specific candidates (using words like “vote for” in ads).

The disclosure requirements, which were supposed to provide some sort of accountability for this spending, haven’t been that successful. It is true that super PACs do have to disclose their donors, and we do learn something from that about who’s funding their ads. But, as is often the case, those who want to spend large amounts of money on politics have found ways around these rules, like setting up 501(c)(4)s or LLCs — which mask donors — that then donate to super PACs. American Bridge Project, for example, is a 501(c)(4) nonprofit that doesn’t have to disclose its donors, and they give large amounts to American Bridge super PAC (in the form of “staff expenses”), which does disclose. Jeb Bush’s super PAC Right to Rise has received $100,000 from an LLC with untraceable origins. Sometimes, of course, these groups don’t even bother with the extra step of giving to the super PAC: a 501(c)(4) called Conservative Solutions has spent millions on promoting Marco Rubio without disclosing any of its donors to the public. If there are any consequences to this, it’s likely they won’t come until after the general election, let alone the primaries.

This election will be only the second presidential election since Citizens United, and the first with no incumbent. By all indications, the 2016 election will be the biggest yet for the unlimited spending by individuals and corporations that Citizens United and Speechnow created: Super PACs have already spent more than $145 million — and it’s only January.