Former Trump aide tells loved ones of plans to plead guilty, cooperate with special counsel This was a “gut-wrenching decision” for the ex-campaign official, a source said.

 -- President Donald Trump’s one-time campaign aide Richard Gates has told family and close friends in a letter sent this morning he plans to plead guilty Friday in the special counsel’s criminal case against him, setting up the potential for Gates to become the latest well-informed Trump insider to assist in the investigation into Russian meddling in the 2016 presidential contest, according to sources close to the matter.

Gates is scheduled to appear before a federal judge Friday to face reduced charges of conspiracy against the United States and lying to federal agents, according to a new court filing.

The potential for a guilty plea could dramatically change the dynamics in the investigation, just one day after special counsel Robert Mueller added a raft of new financial and tax charges to the criminal case against Gates and his longtime colleague, Paul Manafort.

Gates has for weeks been vacillating between fighting the charges and pleading guilty, and remained undecided through much of this week, according to the sources. Legal teams for President Trump and Manafort appeared to be unaware as late as Thursday about Gates’ intentions.

In the letter obtained by ABC News, Gates writes to family and friends “despite my initial desire to vigorously defend myself, I have had a change of heart,” Gates explained. “The reality of how long this legal process will likely take, the cost, and the circus-like atmosphere of an anticipated trial are too much. I will better serve my family moving forward by exiting this process.”

Gates, who has a young family, has endured immense pressure throughout, facing charges that carried the potential for more than a decade in jail, and risking the remainder of his savings. The deal hammered out between Mueller’s team and Gates’ legal team has the potential to spare him jail time.

This was a “gut-wrenching decision” for the 45-year-old former campaign official, a source familiar with his thinking told ABC News. Gates also faced a significant financial burden, the source added.

Despite speculation for weeks that Gates was close to or had made a deal, the source told ABC News, a deal with the special counsel’s team did not come together until the middle of this week, and prior to that deal it had looked unlikely.

The exact terms of the deal are still unclear. The special counsel’s office declined to comment.

“The consequence is the public humiliation, which at this moment seems like a small price to pay for what our children would have to endure otherwise,” Gates said in his letter.

Manafort and Gates pleaded not guilty last fall on all charges stemming from special counsel Mueller's investigation into Russian meddling in the 2016 election and possible collusion between the Trump campaign and Russia.

The first round of charges contained 12 counts: conspiracy against the United States; conspiracy to launder money; serving as an unregistered agent of a foreign principal; false and misleading Foreign Agents Registration Act statements; false statements; and seven counts of failure to file reports of foreign bank and financial accounts. Both charges from the first indictment in Washington and the second round of charges filed Thursday in Virginia center around Manafort and Gates’ past lobbying and financial activities and are not related to their work directly for the Trump campaign.

Manafort emerged as a key figure in Mueller's inquiry because of consulting work he previously did on behalf of the Ukrainian government.

In July 2017, the same month he retroactively registered as a foreign agent because of his lobbying work, the FBI executed a search warrant at Manafort's Virginia home, in connection with the Russia investigation. A source familiar with the matter described armed FBI agents' waking Manafort early in the morning as they knocked on his bedroom door.

Manafort, 68, joined the Trump campaign in March 2016 as its convention manager and was promoted to campaign chairman two months later. He was fired from the campaign by then-candidate Trump in August 2016 amid questions about his foreign business ties.

Gates joined Manafort's international firm, Davis Manafort Partners, in 2006. Gates' connections to Trump before and after the election include leading the campaign's operations at the Republican National Convention in Cleveland and serving as a top deputy to Tom Barrack, who served as chairman on the Presidential Inauguration Committee.

Gates later joined America First Policies, a 501(c)(4) nonprofit created after the election that supports Trump positions. Gates left his role with the group after he was indicted.

Mueller was appointed special counsel in May 2017 by Deputy Attorney General Rod Rosenstein; Attorney General Jeff Sessions has previously recused himself from all matters related to the 2016 presidential election.

In addition to Mueller's investigation, Manafort had been heavily scrutinized by multiple congressional committees conducting their own investigations into Russian meddling. Since his indictment last year, Manafort has stopped cooperating with the congressional investigations.