Lincoln, Neb.-- They pop up time and again during election season - political advertisements sponsored by organizations you've probably never heard of and know nothing about.
Groups known as political action committees (PACs) or super political action committees (SPACs) sometimes pay for those ads.
The ads either attack/support certain political candidates or promote ideological views.
But, it's sometimes unclear who exactly is behind them, or paying for them.
Traditional PACs can only give $5,000 to individual candidates during an election season, represent businesses or ideological interests, and accept only limited monetary donations. They can also work with a campaign or candidate.
But, the game changes with SPACs.
"Now, all those monetary restrictions are off," John Hibbing, a political science professor at the University of Nebraska at Lincoln, said.
"You're no longer limited to $2,500 or $5,000. You can get however much you want."
Hibbing said SPACs can take unlimited contributions from individuals, corporations and even candidates.
The SPACs can then spend the money how they please. They've only been around since 2010, and unlike PACs, are not allowed to coordinate with candidates or campaign strategies.
"The danger here is that unlike PACs," Hibbing said, "where you're simply coordinating spending at a higher level, now we're to a stage where there is no coordination and there also is no responsibility because it is extremely difficult to find out who is giving money to these entities."
SPACs are required, by law, to report their contributions to the Federal Election Commission (FEC). But, it's possible that the name listed under a specific donation is not where the money actually came from. For example, Corporation X could be the name on the donation, but a third party may have given them the money to begin with.
This uncertainty causes a lot of questions and confusion, according to Hibbing.
"This concept that the courts have set up,"Hibbing said, "this notion, this distinction between coordinate and uncoordinated is one that's extremely difficult to identify."
For example, Senate candidate Shane Osborn's campaign recently condemned an ad they say has been linked to a SPAC funded by Senate candidate Ben Sasse's great uncle.
Sasse's campaign claims they haven't been involved in the negative ads.
Similarly, Hibbing said a recent ad attacking governor candidate Jon Bruning raised eyebrows, after accusations were made that it was supported by governor candidate Pete Ricketts and a SPAC run by Ricketts' father.
"I can tell you right now," Pete Ricketts said in a recent news conference, "it's not me and it's not my father."
Hibbing said, however, it's important to not jump to conclusions.
"It's easy to think that coordination is always going on," Hibbing said, "but, a lot of time it isn't.
"There have been times that Super PACs have run ads that a candidate would rather not have been run."
Hibbing said this is likely to continue unless the laws surrounding SPACs change.
"If somebody is running a skirtless ad against somebody else," Hibbing said, "you'd like to know who is responsible for that.
"But, that's very difficult to find out with Super PACs."
Political ads typically say who sponsored/paid for the ad near the end of a given advertisement, typically in small text. That organization can often be researched on the Federal Election Commission website, a link to which is posted in this story's sidebar.