Paul Manafort, a top adviser to Donald J. Trump’s 2016 campaign who was pardoned by the former president at the end of his White House term, is in discussions to return to help with the Republican National Convention, according to two people with direct knowledge of the matter.

Mr. Manafort’s potential role at the party’s convention in Milwaukee has not been decided, and the discussions have gone on for several months.

Mr. Manafort’s possible involvement was first reported by The Washington Post.

A Trump campaign spokesman and Mr. Manafort did not respond to requests for comment.

Mr. Manafort, 74, was closely involved in the 1996 Republican Party convention when Bob Dole was the nominee, and he also worked on the convention in support of Ronald Reagan. Mr. Trump brought him in to help with delegates during his 2016 bid, but Mr. Manafort soon took over running the campaign after Mr. Trump’s initial campaign manager, Corey Lewandowski, was ousted.

Mr. Manafort was dismissed by Mr. Trump later that summer. He became enmeshed in the federal investigation into whether Mr. Trump’s campaign had ties to Russian officials; among other findings, investigators said he shared campaign polling data with a Russian connected to intelligence services there.

Mr. Manafort for many months tried to fend off the charges filed against him by the special counsel, Robert S. Mueller III. Mr. Trump praised him publicly for initially refusing to cooperate with investigators and compared him favorably to Mr. Trump’s former personal lawyer and fixer, Michael Cohen.

“Unlike Michael Cohen, he refused to ‘break’ — make up stories in order to get a ‘deal,’” Mr. Trump posted about Mr. Manafort on Twitter in August 2018. “Such respect for a brave man!”

Mr. Manafort was found guilty in late August 2018 of a range of financial crimes, including tax and bank fraud.

In September 2018, Mr. Manafort pleaded guilty to additional charges brought by Mr. Mueller and agreed to cooperate. But as the case proceeded, Mr. Mueller said that Mr. Manafort had not been truthful in his cooperation, breaching that plea deal.

Mr. Trump pardoned Mr. Manafort over the federal investigation at the end of his presidency, and the two have kept in periodic touch, according to several people familiar with their relationship.

Mr. Manafort was also charged in New York State with mortgage fraud charges, but those were eventually tossed under a double jeopardy law because they were similar to some of the federal charges.

The lawyer who represented Mr. Manafort in that case, Todd Blanche, is now representing Mr. Trump in three of the former president’s four criminal cases. Mr. Manafort is among those who recommended Mr. Blanche to Mr. Trump, according to two people briefed on the matter.