NEW YORK (AP) — Donald Trump is taking his first steps toward raising the massive amounts of money needed for a national presidential race, aiming to broaden his primary insurgency into a full-fledged general election campaign and unite the fractured Republican Party behind him. Trump is reaching out to party heavyweights, hoping to repair his at-times strained relationships with the Republican National Committee and big GOP donors whom he bashed repeatedly during the primaries. On Thursday, his campaign named a finance chairman, Steven Mnuchin, who is chairman and chief executive officer of Dune Capital management LLC, a private investment firm, and previously worked at the New York bank Goldman Sachs. Trump's new efforts include taking pains to reassure party leaders that he wants to help Republican Senate and House candidates, some of whom have expressed major concerns that Trump at the top of the GOP ticket will be a drag on their own campaigns. Members of the celebrity businessman's campaign were to meet with the party's national committee and enter a joint fundraising agreement needed for both his bid and for Republicans to maintain control of Capitol Hill, aides said. "High-dollar donors need to be convinced that Trump is going to be a serious candidate and won't embarrass them," said Charlie Spies, a veteran Republican operative with deep ties to party fundraisers. A pro-Clinton super political action committee that can take unlimited donations from wealthy individuals, companies and unions has already reserved some $90 million worth of advertising for the general election.