Get breaking news alerts and special reports. The news and stories that matter, delivered weekday mornings.

DURHAM, N.C. — Lately, there's been a billionaire on Sen. Bernie Sanders' mind.

Not the anonymous legion of billionaires he's railed about for years — but a real one: former New York City Mayor Mike Bloomberg, whose unprecedented spending is threatening to upend the traditional primary process.

"We believe in old-fashioned democracy: one person, one vote, not billionaires buying elections," Sanders said at a rally here Friday afternoon, fresh off his victory in the New Hampshire primary earlier in the week.

Bloomberg, who jumped into the 2020 race late, didn't even try to compete in the first two primary contests, Iowa or New Hampshire. Nor will he compete in the next two this month, Nevada or South Carolina. He's put vast resources into the delegate-heavy March primaries — namely Super Tuesday, March 3, when the most states (14) and American Samoa vote and a veritable treasure trove of delegates is at stake. More than 1,300 pledged delegates of the 1,991 a candidate needs to secure the Democratic nomination will be awarded that night.

Sen. Bernie Sanders, D-Vt., addresses supporters during a campaign rally in Denver on Feb. 16, 2020. Jason Connolly / AFP - Getty Images

The looming Bloomberg threat has Sanders, the current front-runner in national polls, juggling an election fight on two fronts: maintaining an early states operation to keep his other opponents, also no fans of Bloomberg, at bay while holding rallies and deploying more resources to Super Tuesday states like North Carolina, Texas and Colorado to head off the former mayor.

Sanders and his allies have also steadily upped the frequency and tenor of their criticism of Bloomberg, drawing attention to issues like "stop-and-frisk," a policing strategy that Bloomberg supported for years as mayor of New York that gave police wide authority to detain people they suspected of committing a crime. In practice, it was mostly black and Hispanic men who were stopped. Bloomberg has offered an apology for the strategy, though Sanders surrogate Rep. Alexandria Ocasio-Cortez, D-N.Y., recently told reporters she found his response "insufficient."

"We will not create the energy and excitement we need to defeat Donald Trump if that candidate pursued, advocated for and enacted racist policies like stop-and-frisk, which caused communities of color in his city to live in fear," Sanders said at rally in Nevada on Saturday. "The simple truth that Mayor Bloomberg, with all his money, will not create the kind of excitement and energy we need to have the voter turnout we must have to defeat Donald Trump."

Let our news meet your inbox. The news and stories that matters, delivered weekday mornings. This site is protected by recaptcha

On Sunday, Sanders jabbed Bloomberg with a now-familiar line of attack — accusing him of "trying to buy an election" — at a rally that drew thousands in Denver. The latest edition of Sanders' popular campaign newsletter, "Bern Notice," sent that evening, was devoted entirely to hitting Bloomberg and his record.

By Monday morning, Bloomberg tweeted out a video taking aim at Sanders supporters who have been accused of abusive behavior online. "This type of 'energy' is not going to get us there," Bloomberg tweeted.

His campaign said the attacks were a sign of his success.

"As Mike continues rising in the polls, it's clear that other candidates, including Trump, are getting nervous and going on the attack," Bloomberg campaign spokeswoman Galia Slayen told NBC News.

One progressive strategist said that Bloomberg's candidacy offers Sanders an almost poetic foil — no strategic pivot necessary.

"He's been talking about the millionaires and the billionaires forever and here's a real-life billionaire!" said Rebecca Katz, founder of New Deal Strategies. Katz, once a top adviser to former Senate Democratic Leader Harry Reid of Nevada, now works for insurgent progressive campaigns.

"I don't think he has to prepare," she added. "He was born for this fight."

But North Carolina offers an example of the challenges Sanders may face midbattle: Bloomberg has more than 125 paid staffers on the ground working in eight field offices across the state. Sanders has four field offices, 13 paid staffers, and two-campaign co-chairs.

One of those co-chairs, Jillian Johnson, argued that Sanders' passionate volunteer network, built from the foundation of his bid for the Democratic nomination in 2016, would help bridge any gap.

"There are folks in the city I live in, in Durham, who have been already knocking doors, talking to voters, and studying the message of Sen. Sanders campaign for weeks," Johnson, who is Durham's mayor pro tempore, said. "The power of that movement, and those folks going out into their communities, organizing with real people, is a lot stronger than what a self-funded billionaire can put up."

"Bloomberg really just got here," she added.

Democratic presidential candidate Mike Bloomberg at a campaign event at Buffalo Soldiers national museum in Houston on Thursday, Feb. 13, 2020. Go Nakamura / Reuters

Still, polls suggest Bloomberg's blunt-force strategy is having an effect — he's polling at third nationwide while dogging Sanders in some of the Super Tuesday state polls. And in North Carolina, some of the senator's supporters have taken note of Bloomberg's impact.

"Bloomberg had a little rally today and I saw a lot of black people. Here I don't see as many," former Forsyth County Commissioner Everette Witherspoon told a group of Sanders supporters who had gathered in a Winston-Salem cafe for an early voting event last Thursday.

Earlier in the day, Bloomberg had hosted a similar event and he pitched himself as the person who can defeat Trump, with his deep pockets and moderate message.

"I had a friend that called me this morning — called me and woke me up — and she said there were 800 people there," a canvasser for Sanders, Sally Hirsch, 62, said Thursday of Bloomberg's event. "We've got our battle ahead of us."