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Story highlights

Rubio officials defended the decision to hire the attorney

His Senate office said he went "above and beyond to comply" with Senate ethics rules

(CNN) —  

Marco Rubio made a risky decision three years ago during high-profile immigration talks: He hired as his chief negotiator a corporate attorney who represented clients with a direct stake in the legislation.

The move surprised some on Capitol Hill, given the potential of a conflict-of-interest over hiring Florida lawyer Enrique Gonzalez, a friend of Rubio’s for roughly two decades.

Late in the talks, Gonzalez inserted narrowly tailored provisions in the bill that could have helped clients he had represented, including universities, cruise liners and media companies, according to a review of emails and interviews with multiple sources involved in the negotiations.

At the time, Gonzalez’s firm told the media that he had made a “clean break,” putting to rest questions over any conflict. Yet a few months after the bill passed the Senate in June 2013, Gonzalez returned to his old employer – Fragomen, Del Rey, Bernsen & Loewy – one of the nation’s largest immigration firms.

Sen. Dick Durbin, an Illinois Democrat who negotiated the immigration compromise with Rubio and six other senators, said this week that Gonzalez “changed the nature of our negotiations dramatically.”

“I respected his knowledge of the subject,” Durbin said of Gonzalez in a CNN interview. “But I was also always struggling with his private life and his new public role in the negotiations.”

The untold story of Gonzalez’s role is getting new scrutiny as the presidential campaign season gets into full swing. No debate defines Rubio’s time on Capitol Hill more than the immigration battle, which put him in the crosshairs of his party as he tried to emerge as a dealmaker on the emotional issue yet later abandoned the legislation.

READ: Fact checking Barack Obama, Jeb Bush and Marco Rubio on guns

Rubio has faced a barrage of attacks from super PACs affiliated with his rivals Jeb Bush and Ted Cruz over his role in the 2013 immigration fight. As GOP presidential candidates gather for their next debate Thursday night in South Carolina, the new behind-the-scenes details could give more fodder to his critics.

Responding to questions this week, Rubio’s office said that his hire and role in the talks strictly adhered to Senate ethics rules. Gonzalez contended that he had severed all ties with the firm during the negotiations while divesting his equity in the law practice at the time, something he said went beyond what was required. A top executive at the firm sent out a memo in January 2013 saying there could be “no contacts” between the practice’s lawyers and Gonzalez on policy matters. And Gonzalez said he made no arrangements to return to the practice after his stint with Rubio.

Rubio consulted ethics committee

In January 2013, as he was discussing the new position with Gonzalez, Rubio’s office seemed to have recognized there could be a perception problem.

His office and Fragomen attorney Blake Chisam, who has expertise in congressional ethics matters, were in talks with the Senate Ethics Committee to ensure his hire didn’t violate conflict-of-interest guidelines, according to Gonzalez. After Gonzalez took steps to break ties with the firm, Fragomen officials told their employees not to converse with Gonzalez for assistance on client matters.

Gonzalez declined to be interviewed, but he said in an email that he had no plans to return to the firm when he was negotiating the immigration deal. In a separate background document he provided to CNN, Gonzalez argued there were provisions in the immigration bill that could have also hurt some of his former and current clients. It’s unclear which clients would have been impacted.

“I went to work for Sen. Rubio because I believe in his agenda,” Gonzalez said. “I had severed all ties with my firm and clients, and had no agenda to pursue except the senator’s.”

READ: Marco Rubio postpones fundraiser to attend classified North Korea briefing

Rubio officials defended the decision to hire Gonzalez, saying the office went “above and beyond to comply” with Senate ethics rules and the senator’s own standards.

Alex Burgos, a spokesman for Rubio, said Gonzalez was hired “to get the best possible deal.”

“After the bill died, Mr. Gonzalez returned to the private sector,” Burgos said. “Anyone who is now trying to misconstrue his service in our office years ago is obviously trying to hurt Marco’s presidential campaign.”

Burgos added that Rubio demands “all of our employees comply with the spirit and the letter” of congressional ethics rules.

Gonzalez and Rubio

Yet, Gonzalez returned to his old firm very shortly after the bill passed the Senate and when there was still hope of a bicameral deal with the House.