Story highlights Barry Bennett, who resigned from the Carson campaign late last month, is now advising Trump's top aides in a "volunteer" capacity

Bennett said he approached the Trump campaign to talk about things to keep in mind once Trump becomes the nominee

(CNN) Ben Carson's former campaign manager is now informally advising Donald Trump's presidential campaign, according to Trump's campaign manager.

Barry Bennett, who resigned from the Carson campaign late last month, is now advising Trump's top aides in a "volunteer" capacity, campaign manager Corey Lewandowski confirmed. Bennett also confirmed the development to CNN, characterizing his role in an email as "unpaid and informal."

Bennett said he approached the Trump campaign to talk about things to keep in mind once Trump becomes the nominee -- such as the convention, raising money to pay for the convention, managing delegates, rules and floor fights, and dealing with the party apparatus.

"Your reward is a whole new set of problems" once you win the nomination, Bennett said. "There's no day to rest."

He said over the past few weeks he has become increasingly convinced Trump will be the nominee. "If he wins Iowa, I think he runs the board."

Read More