In its third quarter FEC report in 2011, the presidential campaign of then Rep. Michele Bachmann (R-Minn.) included this line-item expenditure.

The $800 paid to Kent Sorenson for "grassroots coordinating" sat alongside another $400 paid for that purpose and $348 paid for mileage.

This line item, from a February 2012 FEC report from the campaign of Bachmann's opponent Ron Paul, also included money that allegedly went to Sorenson. But it looks a bit different.

At the time, Sorenson was an Iowa state senator, and in the up-and-down race for the Republican presidential nomination that was underway, his conservative credentials made him a sought-after endorsement. When he suddenly and publicly switched his allegiance from Bachmann to Paul in 2011, the Bachmann camp alleged that he'd been paid to do so. Sorenson denied it at first, but eventually pled guilty to concealing expenditures and obstructing justice, admitting that he'd gotten money from Paul's campaign for the switch.

On Wednesday, the other shoe dropped. A key staffer from the Paul campaign, Jesse Benton, was indicted with two others for their roles in allegedly hiding the payments to Sorenson, including by routing a substantial payment to the state senator through the "audio/visual" expense shown above.

The charges against Benton (who now runs a Super PAC focused on supporting Rand Paul's 2016 bid) and his alleged co-conspirators John Tate and Dimitrios Kesari include conspiracy, causing false records, causing false campaign expenditure reports, and lying to the FBI, as when Benton allegedly told investigators: "I am not splitting hairs: Sorenson was not getting paid."

Missing from that list, you'll notice, is "paying money for an endorsement." That's because, according to Larry Noble of the Campaign Legal Center and former chief counsel for the FEC, that's not even illegal.

"It is illegal to falsely report. There is a federal law that prohibits buying votes," Noble said when we reached him by phone. "But I'm not aware of a federal law that would prohibit an endorsement." If a campaign wanted to secure an endorsement with money, they can do so.

"The campaign would have to report it as an expenditure, and they would have to put the purpose of it. I don't believe there's anything illegal about doing that." Sorenson may have been doing some grass-roots coordinating for Bachmann, as the expense was recorded; the description is nebulous enough to be hard to disprove. ("For his endorsement" bears political problems, if not legal ones.) The money was reported. He was being paid; he was an endorser.

For Sorenson, there was an added prohibition. As an elected official in Iowa, he was not allowed to take such payments, which appears to be what prompted his attempt to hide them. It was that obstruction that resulted in criminal charges.

The inevitable question, then, is one raised by the Center for Public Integrity's Carrie Levine. "This case also shows it's relatively simple to hide payments on FEC reports by running them through a contractor," Levine tweeted. Offering payments in exchange for endorsements is likely rampant, and often hard to track. And, if you report it accurately and don't lie to the FBI about the payments, legal.