US Election 2016: Michael Bloomberg's presidential campaign was at a very advanced stage before he pulled out

The billionaire's team had commissioned TV ads, built a website and even vetted a prospective running mate, retired admiral Mike Mullen, the former chairman of the US Joint Chiefs of Staff

Former New York mayor Michael Bloomberg had considered standing as an independent (Reuters)

Former New York mayor Michael Bloomberg laid all the groundwork necessary for a major presidential campaign before abandoning his plans for an independent candidacy over concerns that he might clear a path to the White House for Donald Trump.

Mr Bloomberg had hired dozens of campaign staffers who spent months preparing for his potential presidential run, it has emerged. He paid for strategists to conduct polling in more than 20 states, and opened campaign offices in Texas and North Carolina.

The campaign built a website and commissioned television advertisements promoting the 74-year-old as a pragmatic, centrist technocrat who could solve problems free from the pressures of party ideology, according to details leaked to The New York Times. Planned campaign slogans included: “All Work and No Party”.

The billionaire’s plans were so far advanced that he had even vetted a prospective running mate, retired admiral Mike Mullen, the former chairman of the US Joint Chiefs of Staff. He also discussed his intentions with US Vice-president Joe Biden and the British Prime Minister David Cameron.

The possibility of a Bloomberg candidacy was first raised publicly in January, when Mr Trump was already the Republican front-runner, and socialist Vermont Senator Bernie Sanders posed a serious threat to Hillary Clinton’s dominance of the Democratic primaries.

Were the parties to pick nominees from the far left and right, Mr Bloomberg believed he could make a successful run up the political centre. But now, with Mrs Clinton well on her way to the nomination, his third-party bid might have done little more than sap her support in the election.

In a column published on Bloomberg View on Monday, Mr Bloomberg said he was “flattered” by those urging him to run, and believed he could win several states in November’s general election, “but not enough to win the 270 Electoral College votes necessary to win the presidency.”

Without a majority for Mrs Clinton, Mr Trump or himself, it would fall to a Republican-held Congress to select the next President. “There is a good chance that my candidacy could lead to the election of Donald Trump,” Mr Bloomberg wrote. “That is not a risk I can take in good conscience.”

Thanks to the financial and media empire that bears his name, Mr Bloomberg is worth an estimated $36.5bn (£25.6bn), a personal fortune more than eight times that of Mr Trump’s. Like the property mogul, he intended to fund his own campaign, to the tune of at least $1bn.

The two billionaires have wildly divergent temperaments. Mr Bloomberg accused Mr Trump of conducting “the most divisive and demagogic presidential campaign I can remember, preying on people’s prejudices and fears”.

A 2016 bid would probably have been Mr Bloomberg’s final opportunity to run for high office. Originally a Democrat, he was twice elected mayor of New York on the Republican ticket, but declared himself an independent in 2007, before serving his third and final term.