All five of the impeachment lawyers who were expected to represent former President Donald Trump have called it quits, sources told ABC News.

The team, led by South Carolina lawyer Butch Bowers, resigned in part because of disagreements over how to mount Trump’s defense, the sources said. The lawyers had planned to argue the constitutionality of holding a trial given Trump is now a former president.

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The disagreements over strategy varied, sources told ABC News, but Trump wanted his team to argue there was election fraud, while the lawyers and some top advisers to the former president wanted the focus to remain on the constitutionality of a trial with the president no longer in office.

A source close to the former president described the change as a "mutual decision" between the parties.

Trump was impeached by the House on Jan. 13 on a single article for "incitement of insurrection" following the violent siege at the U.S. Capitol that left one police officer and four others dead and left members of Congress and their staffs fearing for their lives. The insurrection, which took place Jan. 6, was preceded by a Trump rally when he told his followers to head to the Capitol and repeatedly said they should fight for him.

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"The Democrats' efforts to impeach a president who has already left office is totally unconstitutional and so bad for our country. In fact, 45 Senators have already voted that it is unconstitutional. We have done much work, but have not made a final decision on our legal team, which will be made shortly,” Jason Miller, a spokesperson for Trump, told ABC News Saturday.

The Senate trial is scheduled to begin on the week of Feb. 8. Two-thirds of the Senate -- or 67 senators -- would need to vote to convict Trump to be successful. That means 17 GOP senators would need to come to the Democrats' side.

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Sources believe there will be another round of additions to the team in the coming days though the process is nowhere near finalized with just over a week to go. Many attorneys who worked with or represented Trump during the last impeachment trial are declining to defend him in the Senate.

Trump's former top lawyer, Jay Sekulow, who represented him at his first impeachment trial, will not be taking part in this trial. Rudy Giuliani, Trump's personal lawyer, also said he will not be representing the former president after appearing at the same rally that preceded the siege on the Capitol on Jan. 6.

The attorneys in addition to Bowers who will no longer be representing Trump are Deborah Barbier, Josh Howard, Johnny Gasser and Greg Harris.

Sen. Lindsey Graham, R-S.C., who urged Bowers to take the case, told his Senate GOP colleagues on Jan. 21 that Bowers would be representing Trump.

Senate Republicans had asked for a delay in the trial, agreed to by Democrats, following the delivery of the impeachment article in order for Trump to work with his still-forming legal team.

ABC News' Mark Osborne contributed to this report.

Donald Trump's entire legal team quits week before impeachment trial: Sources originally appeared on abcnews.go.com