Mitt Romney has denied claims that he passed over Chris Christie as a vice-presidential choice because of questions about the brash New Jersey governor's political past and his obesity.
A new book about the 2012 election paints an unflattering picture of Mr Romney's relationship with Mr Christie, who is one of the men tipped to succeed him as the Republican Party's candidate for president in 2016.
It was seen as a refreshing change from the polarisation that has beset US politics, and Mr Christie looks set to be overwhelmingly re-elected tomorrow in what is otherwise a staunchly Democrat state.
Senior Republicans believe his no-nonsense style and broad appeal also makes him the party's best chance of reclaiming the White House after eight years of Democrat control.
But new details reported in the book 'Double Down' suggest that Mr Romney's aides found "potential land mines" which could detonate during a 2016 bid.
Campaign staff examined Department of Justice reports from Mr Christie's time as a prosecutor, saying he had given "insufficient, inaccurate, or no justification" for spending taxpayer money on luxury hotel stays.
They also investigated his stint as a lobbyist for a financial trade group at a time when Bernie Madoff, the architect of the largest Ponzi scheme in US history, was a board member.
According to the book, written by the journalists Mark Halperin and John Heilemann and based on hundreds of interviews, Mr Christie's staff failed to provide documentation needed to ease Mr Romney's concerns.
Yet while they were looking into unseen corners of Mr Christie's past, the Romney aides were also focused on a more visible issue: his considerable weight, believed at one point to be around 350lb (25 stone).
The Romney vetters, who noted that Mr Christie was "obese", gave him the unflattering nickname of "Pufferfish".
The issue appears to have stuck with Mr Romney, known for exercising by running up and down the stairs of campaign hotels. "Romney marvelled at Christie's girth, his difficulties in making his way down the narrow aisle of the campaign bus," the book said.
Mr Christie had surgery in February and lost significant weight, but he remains obese. (© Daily Telegraph, London)