The man widely tipped to be a major beneficiary of the first round of formal voting in the Democratic party’s search for a challenger to Donald Trump does not even have his name on the ballot paper. The billionaire former New York mayor Michael Bloomberg has skipped the New Hampshire primary, and yet he could still prove to be one of the contest’s big winners.

Final polls showed the veteran senator Bernie Sanders in pole position in the state, with a pack of “moderates” jostling behind him. That’s precisely the scenario – in which Democratic moderates fail to unite behind a single challenger to Sanders and his message of revolutionary change – on which Bloomberg’s presidential bid is predicated. So long as neither the former vice-president Joe Biden, the former mayor Pete Buttigieg nor the senators Elizabeth Warren and Amy Klobuchar manage to break decisively from the rest of the pack, Bloomberg can see a way to overtake them all.

Even as he stayed away from New Hampshire, the financial media magnate is now a strong presence in the race. He is spending more on TV and online advertising than any candidate in US political history, having already dropped about $350m (£270m) of his vast personal fortune – more than the entire budget of the Trump campaign in 2016. That effort is bearing fruit, as a national poll on Monday showed Bloomberg having moved from statistical nowhere to third place on 15%, behind Sanders and Biden. Another survey showed Bloomberg beating Trump by nine points, a wider margin than for any of his Democratic rivals.

Bloomberg speaking at a rally in Rhode Island last week. Photograph: David Goldman/AP

Bloomberg is not relying on brute financial force alone. On the contrary, his broadcast and social media campaign has been fought with considerable elan. The former mayor, who first won office in New York as a Republican, can claim to have produced the best ad of the Democratic field, one that intercuts archive footage of oratorical flights by past presidents from John F Kennedy to Ronald Reagan to Barack Obama with expletive-laden abuse from the current occupant of the Oval Office. In less than 30 seconds, Bloomberg’s ad makes the case that Trump is unfit to be president.

He’s also told the best joke of the 2020 campaign. Asked whether it would be healthy for a presidential election to be fought between two billionaires, Bloomberg replied: “Who’s the other one?”

That hits at a Trump weak spot: the president is famously insecure about his wealth, boasting of a fortune in the high billions that he does not quite have. Bloomberg, by contrast, is thought to be the 14th-richest person in the world with an estimated fortune of $58bn. Some Democrats believe that the prospect of facing Bloomberg in November would unnerve Trump, that the former mayor would get under his skin.

Trump’s most devoted supporters have certainly picked up that animus. “He’s a blowhole, he thinks he can buy his way into the presidency,” was the assessment of Bloomberg offered by Donna, one of the many thousands of Trump fans who queued in the cold on Monday night to attend a Trump rally in downtown Manchester, staged to ensure the Democrats did not have the New Hampshire spotlight to themselves. “He’s got nothing to offer except billions of dollars. He doesn’t love America.”

Donald Trump acknowledges the crowd at a rally in Manchester, New Hampshire, on Monday. Photograph: Justin Lane/EPA

And yet those billions of dollars are proving effective. Normally skipping the first four state contests would doom a presidential candidacy to failure, depriving it of early momentum and publicity. But by spending at a rate of $38 a second, Bloomberg has ensured his name is mentioned at least as frequently as any of those who’ve spent the last weeks and months trekking through snowstorms to speak in diners and high school gyms across this frozen corner of New England. In the words of David Plouffe, who masterminded Obama’s victorious campaign in 2008: “We’ve never seen anything like it.”

But while getting from zero to 15% in the polls is a serious achievement, Plouffe told MSNBC, “the path from 15% to 30% is 50 times harder”. And for Bloomberg there are multiple obstacles in the way.

The first is race. In New York, Bloomberg maintained a policing policy of “stop-and-frisk”, widely held to be discriminatory towards people of colour. Some assumed that would doom Bloomberg’s bid, not least because African Americans account for a huge chunk of the Democratic primary electorate. And yet that same Quinnipiac poll found Bloomberg’s support among black Americans had leapt from 7% to 22%.

Trump attempted to reopen the controversy on Tuesday, tweeting that Bloomberg was a “racist” and posting a video from 2015 showing the former mayor speaking about stop and frisk. “We put all the cops in minority neighbourhoods. Yes. That’s true,” Bloomberg was recorded saying. “Why do we do it? Because that’s where all the crime is. And the way you get the guns out of the kids’ hands is to throw them up against the walls and frisk them.” Trump later deleted the tweet.

A second brake on Bloomberg’s hopes is surely his own limitations as a candidate. While TV ads can make him look like a titan, the reality can be disappointing – and not only because of his diminutive stature. (Trump has already branded him “Mini-Mike”.) He’s not a charismatic performer, more technocrat than politician. Which is one reason why senior Democrats suspect he will skip participation in the Democratic TV debates, even if he clears the qualifying threshold.

But the primary worry is that should Bloomberg somehow win the Democratic nomination, passionate Sanders supporters could withhold their support, just as many refused to back Hillary Clinton in 2016. Shifting from Sanders, the scourge of Wall Street, to Bloomberg, a luminary of high finance, would surely be a compromise too far.

And yet those waving placards for the Vermont senator at an eve-of-poll rally on a university campus in Rindge on Monday were unexpectedly accommodating towards the billionaire candidate.

Bernie Sanders poses for selfies at at campaign rally in Rindge, New Hampshire, on Monday. Photograph: Mike Segar/Reuters

“He’s competent,” conceded Aquino Loayza, while Brett Zografos said that if Bloomberg were his party’s eventual nominee, “I’d vote for him. He will champion policies that fit with me more than Trump.”

It hardly sounds likely. In fact, everything about Bloomberg’s candidacy is unlikely. But, as the events of the last four years have shown, that’s no disqualification at all.