Following an investigation by The Miami Herald and El Nuevo Herald, FBI agents in August began interviewing campaign vendors who said Rivera was behind Sternad’s campaign.

Alliegro’s involvement in Sternad’s campaign was a red flag. She’s not only a Rivera confidante; she’s a self described “Republican bad girl.” Sternad ran as a Democrat. Technically, if he won the Aug. 14 primary, he would have faced Rivera in the general election.

Sternad lost the primary to Joe Garcia, but not before he began adopting Rivera’s lines of attack against the Democrat, who went on to defeat the incumbent congressman in November.

To get his message out, Sternad received multiple amounts of cash from “co-conspirators,” the federal charging document says. Some of them delivered the stacks of cash on his behalf to campaign vendors to underwrite the cost of targeting voters and designing, printing and mailing a dozen fliers. Sternad reported almost none of the expenditures until The Miami Herald and El Nuevo Herald raised questions about how the blue-collar political neophyte had the sophistication or money to design and send the mailers.

Some mailers targeted environmentalists, immigration hardliners, rural voters and women. Other mailers bearing the phrase “Lamar will take us far” was aimed at black voters and featured only African-American politicians. Sternad’s face was nowhere on the mailers.

After The Herald began investigating Sternad’s campaign, he amended his reports to say he loaned himself about $64,000 instead of the $10,800 he initially reported.

Turns out, Sternad only loaned himself $300. The rest came in unreported cash in amounts ranging from $500 to $22,000 involving three bank accounts.

Sternad — who earns less than $30,000 yearly and has a family of five — has little money in the bank. He often takes the bus to work. Sternad didn’t have a car Friday and had to hitch a ride from the FBI to surrender.

In a sign of near-pity, Assistant U.S. Attorney Thomas Mulvihill spoke on Sternad’s behalf by asking Magistrate Judge Alicia M. Otazo-Reyes to allow the defendant to frequent bus stations. He’s banned from other transportation hubs, such as airports, and had to surrender any travel documents he might have. Sternad also posted a $100,000 personal surety bond.

The conspiracy, the federal government argues, began as early as May 25 when “a co-conspirator hand-delivered $500 cash” to Sternad. He deposited $300 in his campaign account and apparently pocketed the rest.

About two weeks later, his campaign account received two cash infusions totaling $10,500. On the same day he received the last payment, Sternad then paid the qualifying fee to be on the ballot.

Cash was so tight for Sternad that, after “a co-conspirator deposited $1,060 in cash” in his account, he rented a motor vehicle from Enterprise Rent-A-Car to drive the district, the court document says.

In July, Sternad’s campaign began receiving larger and larger unreported cash infusions from unnamed sources. The campaign also began paying an unnamed graphic designer and employees with Expert Printing, known also as Inkpressions, for developing and producing mailers.

In mid-July, “a co-conspirator hand-delivered $10,000, in cash” to Expert Printing. Another $15,901.35 in cash was delivered to Rapid Mail & Computer Service, which helped label and send out the mailers.

Rapid Mail’s owner, John Borrero, told The Herald/El Nuevo Herald that some of the cash was delivered in envelopes stuffed with crisp $100 bills. Borrero also said Rivera was behind the campaign.

Another campaign vendor, Hugh Cochran of Campaign Data, doesn’t appear in the charging document. He helped produce computer data to target voters on Sternad’s behalf. He showed an email to The Herald/El Nuevo Herald indicating that Rivera was directing the mailers on Sternad’s behalf.

Rivera said he was mistakenly emailed by Cochran. And after Cochran said Rivera was behind Sternad’s effort, Rivera accused him of being mentally infirm.

Rivera is simultaneously facing yet another federal investigation, headed up by the IRS, into a $500,000 dog-track contract he secretly engineered to push a successful slot-machine ballot initiative. Rivera has denied wrongdoing in that case. The prosecutor in that case is the same one in this case: Thomas Mulvihill.

On Friday, Mulvihill declined comment. His boss, U.S. Attorney Wifredo Ferrer, issued a written statement: “We are committed to promoting transparency and accountability from our elected officials and from those running for office. Our citizens deserve no less.”

El Nuevo Herald editor Manny Garcia contributed to this article.