Rick Hampson

USA TODAY

NEW YORK — It was less than three years ago that Michael Bloomberg, who’s now thinking about running for president, said that it was “impossible’’ for him or any independent candidate to reach the White House.

A new national poll suggests that he may have been right the first time, and that his candidacy could change the election’s dynamics.

A USA TODAY/Suffolk University poll found that in a hypothetical race with Donald Trump as the Republican nominee and Bernie Sanders leading the Democratic ticket -- presumably the scenario most conducive to a Bloomberg victory -- Trump was chosen by 37% of likely voters, Sanders by 30%, and Bloomberg by 16%.

Without Bloomberg in the mix, Trump and Sanders were in a dead heat — 44% to 43%, within the poll’s margin of error. Bloomberg drew 13 percentage points from Sanders and only seven from Trump.

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The poll addresses a question Bloomberg himself seemed to have settled.

”I am 100% convinced that you cannot win an election unless you are the nominee of one of the two major parties,’’ Bloomberg told New York magazine in 2013, a few months before his third and final term as New York's mayor ended.

A 'vanity candidacy'?

Five years earlier, Bloomberg had decided not to make a 2008 presidential bid, half-joking to friends that the nation wasn’t ready for a short, divorced Jewish billionaire in the White House.

But now Bloomberg says he’s so distressed by the tone of the presidential campaign — “an outrage and an insult to voters’’ — that he’s considering what he so recently and categorically dismissed. And he’s reportedly willing to spend $1 billion of his $41 billion (as per Forbes) to do so.

Bloomberg’s decision, which he’s said he’ll make by early next month, will apparently depend largely on whom the two major parties seem likely to nominate.

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He’s less apt to run if they’re relative centrists like Hillary Clinton and Jeb Bush. But those close to Bloomberg say the strong showing in the Iowa and New Hampshire voting by Sanders, Trump and Ted Cruz has made him more inclined to jump in.

Republicans hope he will. “Please, God!’’ says conservative talk-show host Hugh Hewitt. Pat Buchanan, an aide to three GOP presidents who himself ran as a third party presidential candidate in 2000, cries, “Run, Mike, run!’’

Trump said he’d welcome Bloomberg’s entry and seemed to try to goad him by demeaning his company’s prospects.

Bloomberg’s mayoral record contains much to please (and dismay) Democrats and Republicans, liberals and conservatives. But to the extent that voters outside metro New York know Bloomberg, they may think of him more as the gun control advocate who tried to ban sales of sodas over 16 ounces than a business entrepreneur who backed stop-and-frisk police tactics.

Whatever Bloomberg’s impact on the race, “his chances of winning are very slim,’’ says Walter Stone, co-author of Three's a Crowd, a study of third-party presidential bids. “The deck is stacked against him.’’

Bloomberg has an impressive résumé: a self-made billionaire who founded a global financial information company; a philanthropist who’s given billions; a mayor who presided over historic reductions in crime, helped the city recover from 9/11 and banned smoking in bars.

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He’s also covered all the political bases. Initially a Democrat, he ran in 2001 for mayor as a Republican and declared himself an independent in 2007.

And more than a half of respondents in the USA TODAY/Suffolk poll said they thought the nation needed more than two political parties to represent political views.

Bloomberg’s pollster, Douglas Schoen, says his man has the money, message, independence and time to fill that need: "I don't think the conventional wisdom'' —that Bloomberg is perceived as a New York nanny-state liberal — "is going to last. The mayor would be able to build support rapidly.''

But at this point — before Bloomberg has given a speech or run a TV ad, and when 15% of voters in the poll were undecided about the three-candidate race — Bloomberg’s “looks like a vanity candidacy, not pushed by a public movement, and without a cause,’’ says Geoffrey Cowan, a longtime Democratic Party activist and author of Let the People Rule: Theodore Roosevelt and the Birth of the Presidential Primary. “Who’s demanding that Michael Bloomberg run?’’

If past is prologue ...

Neither history nor logistics are on Bloomberg's side.

Largely because of the winner-take-all nature of the Electoral College, no third-party candidate has ever been directly elected president; none since 1912 has beaten either major party candidate; none since 1968 has won a single electoral vote. That includes Ross Perot, who got 19% of the popular vote in 1992.

The strongest of these doomed efforts had one of three things going for them: a colorful candidate (like Perot); a resonant issue (like the anti-Washington feeling proclaimed by George Wallace in 1968) or a regional base (like the South for “Dixiecrat” Strom Thurmond’s in 1948).

But Bloomberg is a stiff campaigner who managed to get just 51% of the mayoral vote in 2009 despite spending $102 million ($174 a vote). His issue would be his own competence and non-partisanship, hardly a rousing call to arms. His region hasn’t produced a president since 1960, and its loyalty might be claimed by one or more of his rivals (Sanders, Clinton, Trump).

Nor is it clear that Bloomberg is the perfect centrist. He’s a more dedicated proponent of gun control than many Democrats, and a more enthusiastic defender of Wall Street than many Republicans.

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As if all this weren’t enough, Stone says the increase in polarization and partisanship that Bloomberg decries also makes his election even less likely.

That’s because the more politics gets polarized, the more voters fear the candidate at the pole farthest from them. As Election Day nears, Stone says, the number of real independents — always exaggerated to begin with — shrinks, as those in the middle flee to the poles toward which they were actually leaning all along.

In this vision, voters for whom a Trump presidency is the worst possible result flee to Sanders because they’re not willing to risk wasting their vote on Bloomberg; voters for whom a Sanders victory is anathema do the opposite.

Which helps explain why Schoen, the Bloomberg pollster, admits it’s vital that any third-party candidate make voters feel victory is possible.

It’s easy to see why Bloomberg is tempted to run, given his enormous ambition and low threshold for boredom. For 12 years, he had what is often described as the nation’s second biggest job. In the New York magazine interview in 2013, he admitted that philanthropy — even on his own heroic scale – would not be enough to keep him satisfied after leaving Gracie Mansion.

Cowan, who’s studied Theodore Roosevelt’s third-party presidential bid in 1912, is reminded of how lonely, isolated and irrelevant TR felt after leaving the White House in 1909. If Bloomberg ran, he says, “for at least six months, he’s no longer irrelevant.’’

Bloomberg turned 74 on Valentine’s Day. This would almost certainly be his last shot at an office he’s wanted to hold since he was a teenager.

The last man to mount a major third-party presidential race doesn’t think Bloomberg will take it.

“We’ve talked about it in the past, and I believe him when he says he’d only be in it to win, not to be a spoiler or make points,’’ says Ralph Nader, still excoriated by Democrats for tipping the 2000 election to George W. Bush.

But Nader, like many others, thinks Bloomberg’s timing is bad. Sanders, Trump, Cruz and Ben Carson were ahead in recognizing the bull market in political outsiders — a sad irony for a man whose prescience in business made him rich enough to seek the office of which he always dreamed.