“This morning Paul Manafort offered, and I accepted, his resignation from the campaign," Trump confirmed in a statement. "I am very appreciative for his great work in helping to get us where we are today, and in particular his work guiding us through the delegate and convention process. Paul is a true professional and I wish him the greatest success.”
Manafort's resignation comes just two days after Trump hired Kellyanne Conway as his campaign manager and Steve Bannon as his campaign's CEO.
Senior level sources in Trump's campaign told ABC News that Trump debated axing Manafort last week. Now with new campaign team leadership in place, one senior aide said it was "writing on the wall" that Manafort would leave.
Manafort was hired by Trump in March as a convention manager, tasked with helping the real estate mogul secure the Republican nomination. Although he was working for a candidate who pegged himself as an outsider, Manafort was known among the Washington establishment for having advised other GOP presidential nominees including Ronald Reagan, John McCain, George H.W. Bush and George W. Bush.
In May, Manafort took on a new role as campaign chairman and chief strategist. He ran the campaign after former campaign manager Corey Lewandowski was ousted in June.
Hillary Clinton's campaign manager Robby Mook called Manafort's resignation a "clear admission" of Manafort's ties to Russia.
"Paul Manafort’s resignation is a clear admission that the disturbing connections between Donald Trump's team and pro-Kremlin elements in Russia and Ukraine are untenable," Mook said in a statement released today. "But this is not the end of the story. It’s just the beginning. You can get rid of Manafort, but that doesn't end the odd bromance Trump has with Putin."
Ukrainian officials say that Manafort's name appears in "black accounts" linked to the country's former pro-Russian president. Manafort hasn't publicly commented on the ledger but has called the notion that he received cash payments "unfounded, silly and nonsensical."
Trump has suggested he would have a good relationship with Russia's Vladimir Putin and suggested -- sarcastically, he says -- that Russian hackers find Hillary Clinton's emails.
ABC’s Meghan Keneally and Patrick Reevell contributed to this report.