Late last year, Durham, North Carolina, business owner Greg Lindberg wrote a check for $1 million — at the request of Lt. Gov. Dan Forest — to Truth and Prosperity, a super PAC that was created to elect Forest. Lindberg also signed a $1.4 million check to the Republican Council of State Committee, a political spending group that supports other GOP elected officials and that Forest runs.

We know this because Forest took the unusual step of acknowledging that he raised the money from Lindberg on behalf of these groups, which under state law are allowed to rake in unlimited funds from individuals, corporations, and unions as long as they remain "independent" of candidates' official campaigns. In its landmark 2010 Citizens United decision, the U.S. Supreme Court lifted limits on corporate money in politics and enabled such groups to flourish. The Court cited an earlier ruling that said the groups' independence "alleviates the danger that expenditures will be given as a quid pro quo for improper commitments from the candidate."

But as the Forest case shows, exactly what constitutes "independence" remains murky. In response to the revelations, Bob Hall, former head of the elections watchdog group Democracy North Carolina, asked the state elections board to prohibit candidates from raising unlimited sums for super PACs. Doing so "risks unacceptable political pressure and corruption," he said in his letter, because the super PAC becomes "merely a device for the candidate to circumvent the campaign contribution limits."

Citizens United led to the creation of super PACs that have no contribution limits, and these independent spending groups have become much more powerful. By 2016, they were spending 77 times more on federal elections than they did before the ruling. They are also increasing the influence of wealthy donors: The top 20 donors in the 2016 federal elections accounted for more than $500 million of this money.

Independent spending has also dominated recent high-profile elections in the South. Two D.C.-based super PACs set up a third to spend $4 million last year to help elect Democrat Doug Jones of Alabama to the U.S. Senate. In Virginia, a state that does not limit direct campaign contributions, both candidates in last year's gubernatorial election received millions of dollars from independent groups. And in the 2017 Georgia special election for the U.S. House, both  candidates were backed by big spending from super PACs.

In North Carolina and Virginia, electric utilities Duke Energy and Dominion Energy have contributed millions of dollars — not only to state legislators' campaigns, but also to the super PACs that help elect them. In 2014, for example, Duke gave larger-than-usual contributions to two Republican independent spending groups just as North Carolina legislators were weighing how to respond to coal ash threatening water supplies.

This barely regulated political spending is now beginning to affect state courts, where most judges are elected. In 2016, three independent spending groups invested more than $1 million in a North Carolina Supreme Court election. And a Virginia-based group that does not disclose its donors spent $1.7 million on judicial races in Louisiana and Mississippi, according to the Brennan Center for Justice and the National Institute on Money in State Politics.

A few states have responded to the explosion in independent spending with new rules to keep candidates from essentially running their campaigns through such groups. A 2014 Brennan Center report concluded that these states "have embraced promising new policies to enforce the actual independence of unlimited spending." But in many states, "laws meant to deter coordinated spending are too ambiguous, narrow, or weakly enforced."

There have been few efforts by legislators or regulators in Southern states to toughen the rules for super PACs. Some states, including North Carolina, passed tougher laws on political spending after Citizens United, only to see regulators interpret them narrowly.

Shortly after the ruling, North Carolina revised its laws to redefine campaign contributions as money donated "in coordination with a candidate," and it defined coordination as something done "at the request" of a candidate. Contributions that meet this definition are limited to $5,200, which Hall says Forest exceeded when he solicited the $1 million check from Lindberg to the super PAC. But to date, the state elections board has interpreted the 2010 law to allow candidates to raise funds for the supposedly independent PACs supporting them, as long as they do not to work together on spending the money.

Campaign finance reform advocates make the case that super PACs devoted to a single candidate, like Forest's group, increase the risk of coordination. A report by elections law experts Renata Strause and Dan Tokaji includes interviews with political campaign staffers who "expressed suspicions or repeated rumors that their opponent had coordinated illegally with a friendly outside group, although most were also quick to acknowledge they lacked hard evidence to back up the claim."

These "single-candidate" super PACs are often run by former campaign staffers or friends of the candidates. One such group, Florida Gov. Rick Scott's super PAC, raised $28 million to reelect him in 2014. Florida law allows candidates to coordinate with super PACs on fundraising and even spending on ads, as long as the ads do not explicitly tell viewers or readers to vote for or against a candidate. Scott's super PAC ran ads attacking the record of his opponent, a former governor.

As this unprecedented amount of money flows into and out of super PACs, states are also seeing more advertisements that look like campaign ads from secret money groups that can accept unlimited contributions — without disclosing where their funding came from. These are nonprofits that are supposed to focus mostly on "social welfare" or other philanthropic issues and not electoral politics. Among the most well-funded of these groups is the Koch brothers' Americans for Prosperity, which spent $122 million to influence the presidential and congressional elections in 2012 alone. Few states in the South have strong disclosure laws related to such groups, and North Carolina actually weakened its disclosure rules in 2013.

With the Federal Elections Commission and Congress too mired in gridlock to act, the problem of unlimited campaign cash can and should be addressed at the state level. States can move forward now. This is particularly important since the South will see a number of high-profile governors' races this year. At the same time, court rulings on gerrymandering could lead to more competitive elections in Virginia and North Carolina, and more competition is likely to attract more money.

Cracking down on unlimited political contributions would help ensure that elected state officials are responsive to their voters — not just donors with deep pockets.