Donald Trump's campaign chairman Paul Manafort has resigned. The news, first reported by the Washington Post, was confirmed by a statement Friday morning from the Republican nominee.

"This morning Paul Manafort offered, and I accepted, his resignation from the campaign. 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," said Trump in his statement.

Manafort had been effectively demoted earlier in the week with the tapping of pollster Kellyanne Conway as campaign manager and Breitbart News chairman Stephen Bannon as campaign CEO—though the official explanation from Team Trump was that the shuffle was an "expansion."

Manafort's controversial lobbying work for unsavory foreign actors and governments had been under scrutiny since the campaign brought on the veteran GOP operative in March. But this week, numerous reports revealed Manafort's lobbying on behalf of the pro-Russian ruling party in Ukraine involved failing to register as foreign agents, per federal law, and receiving off-the-books cash payments of more than $12 million. Manafort, for his part, has denied receiving cash payments for his work on behalf of the now-deposed president of Ukraine Viktor Yanukovych, a geopolitical ally of Russian president Vladimir Putin.

And there remain questions about whether Manafort and his firm have continued to work on behalf of the pro-Putin forces in Ukraine. At the Republican National Convention, for instance, delegates on the platform committee say Trump campaign operatives influenced a change in the GOP platform that called for less American aid to pro-Western Ukrainians fighting Russian forces there.

When he joined the Trump campaign in the spring, Manafort was seen as someone who could professionalize the skeletal operation as it moved from the primary period to the general election. A veteran of past presidential campaigns, including Gerald Ford's 1976 reelection bid and Bob Dole's 1996 run, Manafort was reportedly encouraging Trump, privately and publicly, to pivot to a more palatable style and presentation. Although the convention in Cleveland and a series of policy speeches suggest he had some success at this endeavor, Trump's unwillingness to "pivot"—by engaging in days-long fights over the Mexican-American judge overseeing the Trump University lawsuit and the Muslim Gold Star parents who publicly endorsed Hillary Clinton, for example—revealed Manafort's influence was only partial.

According to Maggie Haberman of the New York Times, Rick Gates, Manafort's business associate, will remain with the Trump campaign.

Update: Bloomberg's Kevin Cirilli reports Gates has also left the Trump campaign.

Update II: Bloomberg's Jennifer Jacobs reports Gates is remaining with the campaign after all.