Michael R. Bloomberg, who for months quietly laid the groundwork to run for president as an independent, will not enter the 2016 campaign, he said Monday, citing his fear that a three-way race could lead to the election of a candidate he thinks would endanger the country: Donald J. Trump.
In a forceful condemnation of his fellow New Yorker, Mr. Bloomberg said Mr. Trump had run “the most divisive and demagogic presidential campaign I can remember, preying on people’s prejudices and fears.” He said he was alarmed by Mr. Trump’s threats to bar Muslim immigrants from entering the country and to initiate trade wars against China and Japan, and he was disturbed by Mr. Trump’s “feigning ignorance of white supremacists,” alluding to Mr. Trump’s initial refusal to disavow support from David Duke, a former Ku Klux Klan leader.
These moves would divide us at home and compromise our moral leadership around the world,” Mr. Bloomberg said in a column published Monday on Bloomberg View, his opinion site. “The end result would be to embolden our enemies, threaten the security of our allies, and put our own men and women in uniform at greater risk.”
The decision by Mr. Bloomberg, who served three terms as the mayor of New York, ends months of intensive preparation for a candidacy. Convinced that a restive electorate was crying out for nonpartisan, technocratic government, he instructed his closest aides to set up the machinery for a long-shot billion-dollar campaign that would have subjected his image to a scorching political test.
They covertly assembled several dozen strategists and staff members, conducted polling in 22 states, drafted a website, produced television ads and set up campaign offices in Texas and North Carolina, where the process of gathering petitions to put Mr. Bloomberg’s name on the ballot would have begun in days.
Mr. Bloomberg held extensive talks with Michael G. Mullen, the retired admiral and former chairman of the Joint Chiefs of Staff, about forming an independent ticket. Lawyers for Mr. Bloomberg had completed the process of vetting Mr. Mullen, and all that remained was for Mr. Bloomberg to ask formally that Mr. Mullen serve as his running mate.
Torn between his aspiration and a mountain of data showing that the path for an independent campaign aimed at the political center was slim and narrowing, Mr. Bloomberg, 74, ultimately abandoned what would probably have been his last chance to run for the White House.
Had both Mr. Trump and Senator Bernie Sanders of Vermont appeared headed toward victory in the Republican and Democratic presidential primaries, Mr. Bloomberg was determined to run, according to his advisers, several of whom insisted on anonymity to speak candidly about confidential discussions.
But Mr. Bloomberg balked at the prospect of a race against Mr. Trump and Hillary Clinton, who has established a dominant lead over Mr. Sanders on the Democratic side. In his column, Mr. Bloomberg said he could not in good conscience enter a race that could lead to a deadlock in the Electoral College — and to the election of Mr. Trump, or perhaps Senator Ted Cruz of Texas.
Mr. Bloomberg’s decision brings a new measure of clarity to a race that has come sharply into focus in recent weeks, and reflects both Mrs. Clinton’s tightening grip on the Democratic contest and the growing alarm among mainstream political and business leaders about Mr. Trump’s populist insurgency.
Mr. Trump is widely seen as a weak general election candidate, and surveys conducted for Mr. Bloomberg bolstered that perception. Mr. Bloomberg’s veteran pollster, Douglas E. Schoen, gauged his prospects in polls in February and March, testing Mr. Bloomberg as a candidate nationally and in 22 crucial states.
At the outset, about two-fifths of the country had no familiarity with Mr. Bloomberg, who may be best known nationally for his support of expanded gun control legislation. But Mr. Schoen’s February polling found that after voters heard mostly favorable descriptions of Mr. Bloomberg, Mr. Trump and Mr. Sanders, Mr. Bloomberg collected 35 percent of the vote and a solid lead in the Electoral College. In a race against Mr. Trump and Mrs. Clinton, however, Mr. Bloomberg faced far tougher odds.
The most favorable result for Mr. Bloomberg might have been a stalemate in the Electoral College, with no candidate capable of taking the 270 votes required. Under those conditions, the House of Representatives, where Republicans hold a majority, would choose the president.
A second poll, taken by Mr. Schoen from Feb. 28 to March 1, found that Mr. Trump was bleeding support with general election voters after a flailing debate performance and a disastrous interview in which he failed to disavow Mr. Duke’s support.
Still, the poll found Mr. Bloomberg could overtake Mr. Trump and fall short of eclipsing Mrs. Clinton.
Mr. Bloomberg acknowledged that cold math in his column. “I believe I could win a number of diverse states,” he wrote, “but not enough to win the 270 Electoral College votes necessary to win the presidency.”
By opting not to run, Mr. Bloomberg is deactivating a political apparatus far more extensive than the one he assembled the last time he seriously weighed a run for president, in 2008. In private conversations, Mr. Bloomberg appeared far more enthusiastic about running now, and he laid out his ambitions in conversations with leaders including Vice President Joseph R. Biden Jr. and Prime Minister David Cameron of Britain.
Aides planned an elaborate campaign to introduce him to the electorate, and consulted with Milton Glaser, the architect of the “I Love New York” campaign, and the Swedish industrial designer Thomas Meyerhoffer to work on logos.
His messaging would have stressed Mr. Bloomberg’s identity as a self-made man and a problem solver not beholden to either party. A draft of his website carried the slogan, “All Work and No Party.” One logo, etched in purple, read simply: “Fix It.”
A rough cut of a presidential campaign ad described Mr. Bloomberg as the product of middle-class Medford, Mass., who built a multibillion-dollar enterprise from scratch. It cast Mr. Bloomberg as a philanthropist who had given generously to fight deadly diseases, and highlighted his experience managing New York’s security after the Sept. 11, 2001, attacks.
“Finally, a new choice,” the commercial’s narrator says. “Independent Mike Bloomberg: President.”
Trevor Potter, the election lawyer who was counsel to Senator John McCain’s 2008 presidential campaign, was retained to assemble legal teams to handle local and state ballot-access issues, and address constitutional questions that could arise from an inconclusive result in the Electoral College.
A ballot-access consultant, Michael Arno, leased nearly a dozen offices in Texas and North Carolina to begin gathering signatures to place Mr. Bloomberg on the ballot in all 50 states and the District of Columbia.
For Mr. Bloomberg, the decision drops the curtain on a long-held dream.
In announcing it, Mr. Bloomberg said he expected to serve in other ways. “For most Americans, citizenship requires little more than paying taxes,” he wrote. “But many have given their lives to defend our nation — and all of us have an obligation as voters to stand up on behalf of ideas and principles that, as Lincoln said, represent ‘the last best hope of earth.’
“I hope and pray I’m doing that,” he wrote.
