Sources within the campaign said that Trump will name Paul Manafort to the new role of Campaign Chairman and Chief Strategist.
Campaign spokesperson Hope Hicks confirmed the move, adding that Lewandowski will, “continue overseeing day to day operations and will work with Manafort on political strategy and communications, among other things, through the general election."
Manafort is arguably more from the establishment than most of Trump's relatively young staff, who helped the Republican front-runner in early primary victories.
His particular experience is relevant to Trump's position. Manafort played a significant role in the 1976 convention where Gerald Ford ended up winning the nomination in spite of a fight from Ronald Reagan and Bob Dole.
In later years, Manafort went on to work for Reagan and George H.W. Bush.
Manafort was on Capitol Hill earlier today meeting with Republican leadership.
“There’s a growing number of people supporting us. We feel very comfortable that even more will be supporting us next trip,” Manafort told ABC News. “They all recognize now that we definitely can win, and they want to know what kind of issues we will be stressing, which we’ll be doing in the next month or two."
Trump will be returning to the campaign trail with a rally today in New Jersey that will also serve as a fundraiser for Governor Chris Christie.
ABC News' Ali Weinberg contributed to this report.