Within two years, he had compiled a client list that included General Motors, Experian, the American Hospital Association, AT&T, Eli Lilly, Nextel, Novartis, Pfizer and Fannie Mae, the quasi-governmental mortgage lender whose late entry into the subprime housing market exacerbated the 2008 financial crisis.When Mr. Ricchetti backed Hillary Clinton’s 2008 presidential campaign, aides to her rival for the Democratic nomination, Mr. Obama, seized on Mr. Ricchetti’s $120,000-a-year contract with General Motors. The Obama campaign connected his work to an $8 million earmark Mrs. Clinton secured for the company’s New York operations as a senator, a claim Mr. Ricchetti has denied.But Mr. Ricchetti, whose discursive and regular-guy style mirrors Mr. Biden’s, was viewed with skepticism in the Obama White House even after he had satisfied the two-year lobbying cooling-off period required by Mr. Obama’s policy. When Mr. Biden settled on Mr. Ricchetti to help run his office in late 2011, the White House aides Jim Messina and David Plouffe flatly rejected the idea, according to people close to the situation.A short, intense scrap ensued, ending only when Mr. Obama gave into Mr. Biden’s argument that he had the “right” to pick his own top deputy, several former aides recalled.Mr. Ricchetti was hired and by late 2013 was officially appointed Mr. Biden’s chief of staff. Over the next few years, he essentially took control of Mr. Biden’s post-presidential life, setting up a network of nonprofits and academic institutions that would serve as a base of operations, negotiating the former vice president’s lucrative book deal, and, most important, helping to set up the initial structure of the 2020 campaign, according to aides and Biden associates.While the campaign’s internal policy allows consultants like Mr. Ricchetti to continue receiving outside income from approved sources like his consulting arrangement with AT&T, some of Mr. Biden’s top advisers have begun leaving the influence industry to join the campaign, and possibly a future administration.