Trump "will work with leaders of the Republican Party and various committees to help raise money for them as part of the overall ticket," Manafort told CBS' "Face the Nation."
"Once he is the nominee of the Republican Party, [Trump] has further responsibilities besides his own candidacy," Manafort said. "He is the head of the ticket and he is committed to making sure that Nancy Pelosi is never Speaker of the House again and that Harry Reid and Chuck Schumer remain in the minority of the Senate."
Manafort's plan to make Trump into a party fundraiser could be tricky for the billionaire, who has self-funded his primary campaign.
Part of Trump's appeal to voters is that he appears to be a financially independent candidate, and not beholden to wealthy campaign donors. During campaign rallies, he regularly denounces the influence of "special interests" and "Washington lobbyists," and accuses his opponents of serving the interests of their campaign donors.
If Trump were to lead a national GOP fundraising campaign, his image as a maverick who bucks the party system could be difficult to maintain.
Moreover, this scenario presumes that GOP candidates would even want Trump to come to their districts and help rally their constituents. Some candidates, especially vulnerable Republicans in swing states, like Ohio Sen. Rob Portman or Illinois Sen. Mark Kirk, might prefer that Trump stay far away from their campaign events.
Since announcing his candidacy for president last year, Trump's penchant for vicious insults and his racially tinged, nationalist rhetoric have helped drive his negative ratings to record highs. And its not just Trump. This week, a new Pew Research Center poll found that unfavorable opinions of the Republican party are around 62 percent, the lowest levels since 1992.
In the coming weeks, Trump's campaign hopes to start unifying the GOP around the front-runner. "We've got a series of meetings that we're planning starting after Tuesday, after the Indiana primary when we believe everybody in the country will recognize that Donald Trump will be the nominee of the party," Manafort told CBS.
If Trump wins the nomination without tapping into the nationwide network of top Republican contributors, as it looks increasingly likely he will, his campaign could be faced with a Herculean task. How to create a national fundraising operation from scratch, capable of raising up to a billion dollars to help Trump mount a 50 state campaign.
As of this week, Manafort said the Trump campaign hadn't decided what kind of money, or how much, it would accept from outside donors.
"Certainly if he is going to be getting money from donors as a general election candidate, there are limitations," he said. "But we haven't dealt with that issue yet."
Trump also hasn't yet begun the process of combining his campaign's fundraising with that of the Republican National Committee. At this point in the 2012 presidential campaign, Mitt Romney's campaign already had a joint account with the RNC.