The former President and RNC Chairwoman allegedly exchanged threats on Trump’s last day.

ABC News’ Chief Washington Correspondent Jonathan Karl has published a new book detailing the last days in office of former United States President Donald Trump. The book, entitled “Betrayal: The Final Act of the Trump Show,” alleges that Trump intended to leave the Republican party entirely following the end of his run in office and start his own party, but was forced to back down by Republican National Convention Chairwoman Ronna McDaniel.

A new book by John Karl, "Betrayal: The Final Act of the Trump Show" reveals conversations between former President Donald Trump and RNC Chairperson Ronna McDaniel over whether Trump would break away from the GOP and form his own party. https://t.co/mH1sgETbYB

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“[RNC Chairwoman Ronna McDaniel] called to wish him farewell. It was a very un-pleasant conversation,” the book, which is scheduled to release on November 16, reads.

“I’m done,” Trump told McDaniel. “I’m starting my own party.”

“You cannot do that,” McDaniel told Trump. “If you do, we will lose forever.”

“Exactly. You lose forever without me,” Trump responded. “I don’t care.”

"Betrayal" book: Trump threatened to leave GOP but backed down after RNC threat

Former President Trump told the Republican National Committee chair that he was leaving the GOP to create his own new political party, according to a new book by ABC's Jonat… https://t.co/Cu0s8jF77q

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“But, more significant, the RNC threatened to render Trump’s most valuable political asset worthless,” the book explains, referring to “the campaign’s list of the email addresses of forty million Trump supporters.”

“It’s a list Trump had used to generate money by renting it to candidates at a steep cost,” the book continues. “The list generated so much money that party officials estimated that it was worth about $100 million.” It is with a threat to withhold this campaign list that McDaniel convinced Trump to back down on his threat and remain a republican.

Both Trump and McDaniel have denied the claims in Karl’s book, asserting that they had and continue to have a good relationship.