Paul Manafort, Donald Trump’s campaign chairman, has resigned, the campaign announced in a statement Friday.

“This morning Paul Manafort offered, and I accepted, his resignation from the campaign,” Trump said. “I am very appreciative for his great work in helping to get us where we are today, and in particular his guiding us through the delegate and convention process. Paul is a true professional and I wish him the greatest success.” 

Manfort’s role in the campaign was reportedly diminished this week with the Republican presidential nominee naming longtime adviser Kellyanne Conway as campaign manager and Breitbart’s Stephen Bannon as chief executive.

Trump told The Wall Street Journal that he was making the changes because “I want to win. That’s why I’m bringing on fantastic people who know how to win and love to win.”

Friction reportedly developed between Manafort and Trump over the campaign’s direction as his poll numbers fell against Democratic rival Hillary Clinton.

Manafort himself has been a distraction to the campaign over questions about his previous business dealings in Ukraine. 

[A Dangerous Gig: Working for Paul Manafort]

The Associated Press reported Wednesday that Manafort helped a pro-Russia group in Ukraine secretly route more than $2 million in payments to two Washington lobbying firms to try to influence U.S. policy.

On Friday, the AP reported that emails showed Manafort’s company led the effort to sway American public opinion in favor of Ukraine’s pro-Russian government.

According to the AP, Manafort and his deputy Rick Gates tried to gain positive coverage of Ukrainian politicians in newspapers like The New York Times and The Wall Street Journal.

The report also said Gates, who worked for Manafort at the time, directed Washington, D.C., law firms Mercury LLC and the Podesta Group to set up meetings between Ukrainian officials and members of Congress.

The Podesta Group was co-founded by Tony and John Podesta, who now serves as campaign chairman for Clinton.

The New York Times reported this week that handwritten ledgers designated $12.7 million in payments to Manafort from the pro-Russian party of former President Viktor Yanukovych.