Mike Bloomberg still introduces himself to voters on the stump by saying “I’m an engineer” — an egghead identity he honed managing large organizations like the city of New York, his namesake company and a nascent presidential campaign now on track to spend more than any other in U.S. history.

But Wednesday night, Bloomberg will be forced to leave his comfort zone and test his chops as a charismatic politician. When he steps onto the debate stage in Las Vegas for his first hostile and uncontrolled campaign test, there will be no management decisions to make, teleprompters to lean on or endless ad budgets to filter his image with focus-grouped messaging.

In preparation, his advisers have spent much of the past week drilling him for the big jump, which could make or break the momentum he has generated with his extravagant spending. In debate prep sessions, they have armed him with comebacks for the inevitable attacks on his enormous wealth and past record, while also coaching him to move beyond his sometimes distant, wonky and diffidently logical public persona.

“Mike is the most deeply steeped student of policy who is going to be on that debate stage,” said Bloomberg senior adviser Tim O’Brien, one of many who have helped the candidate prepare for the debate. “We also really hope voters get to see his humanity and his compassion.”

Wary of Bloomberg’s rise in the polls, his rivals, with far more debate experience and Democratic longevity, have made clear that they will not go easy on the newcomer.

Sen. Bernie Sanders (I-Vt.) spent Tuesday in Reno, Nev., denouncing Bloomberg’s campaign as an example of “oligarchy, not democracy.” Former vice president Joe Biden has been boasting for days about his desire to confront Bloomberg in person because he cannot compete with the billionaire’s advertising budget.

“At least now primary voters curious about how each candidate will take on Donald Trump can get a live demonstration of how we each take on an egomaniac billionaire,” Sen. Elizabeth Warren (D-Mass.) warned in a tweet about Bloomberg on Tuesday.

The scrutiny comes as Bloomberg’s aides are attempting to reframe the contest as a two-person race, between Sanders and Bloomberg, after several state and national polls have shown Biden’s support plummeting as the former New York mayor rises past Warren, Sen. Amy Klobuchar (D-Minn.) and former South Bend, Ind., mayor Pete Buttigieg.

In a call with reporters Tuesday, Dan Kanninen, Bloomberg’s states director, said Sanders was the only other viable Democrat in the race. He said supporters of other candidates need to quickly choose between the two or risk wasting their votes in upcoming primaries. Under party rules, candidates who get less than 15 percent of the vote in a state or congressional district are awarded no delegates.

Multiple recent polls have found both men on the ascent in the Democratic race — and on a collision course if their trajectories continue. An NBC News-Wall Street Journal poll published Tuesday put Sanders at 27 percent and Bloomberg at 14 percent, one point below Biden at 15 percent. Unlike Biden, who fell 11 points in the past month, Bloomberg gained five points over the same period.

But a race between the two at the current moment would be no contest, with Sanders at 57 percent and Bloomberg at 37 percent.

“It’s very clear Democrats have to urgently consolidate around a candidate,” Kanninen said, warning that supporters of other moderates could inadvertently help nominate Sanders by refusing to get behind Bloomberg on his timetable. “There really is a prospect of a candidate with maybe only a quarter of the votes getting 80 to 90 percent of the delegates.”

Bloomberg’s rise in polling comes as he faces a barrage of negative news coverage, some of it promoted by rival campaigns. He has had to again address allegations that he made vulgar and sexist comments, his past defense of targeting stop-and-frisk police policies to black and Latino neighborhoods in New York, and an interview in which he blamed the 2008 financial crisis on politicians who had pushed to end racially discriminatory mortgage-lending policies known as “redlining.”

Bloomberg’s past political leanings — he re-registered as a Democrat only in 2018 — and his refusal to file a financial disclosure or release his tax returns before the debate, even as he is self-financing his campaign, also could come into play Wednesday. A spokesman for his campaign said the financial disclosure would be filed by March 20, and Howard Wolfson, a senior adviser to the campaign, has previously said Bloomberg would release his tax returns, though no date has been set.

Bloomberg campaign manager Kevin Sheekey signaled Tuesday that the campaign may soon adopt a more aggressive posture toward opponents like Sanders.

“The opposition research on @BernieSanders could fill @realDonaldTrump’s empty Foxconn facility in Wisconsin,” Sheekey wrote in a Twitter post, with no elaboration save the reference to a giant manufacturing space for which President Trump once claimed credit. “It is very damaging, perhaps even disqualifying.”

Those comments and the campaign’s new get-it-done thrust came less than a week after Bloomberg declined to criticize Sanders or express concern about a lack of consolidation among the moderate Democratic candidates.

“I’m not a prognosticator, so I don’t want to comment on who’s up and who’s down,” Bloomberg said last week on a tour through Tennessee, demonstrating his typically dispassionate style. “I believe that I have common-sense policies that are affordable, practical and politically viable to take this country forward.”

Until now, Bloomberg has built a campaign that exists overwhelmingly in the realm of paid advertising, with hundreds of television and digital ads that have been tested and refined to produce positive responses from their audience.

Through mid-February, Bloom­­berg has spent about $339 million on television and radio, more than the total that Barack Obama spent on such ads during his 2012 reelection campaign, according to Advertising Analytics, a tracking firm. By comparison, the two top finishers in the Iowa caucuses, Buttigieg and Sanders, spent more than $10 million each on broadcast advertising in the state.

To put the spending in another context, all the ads Bloomberg purchased through Feb. 10 would run for 4,106 hours, or 171 days, if they were played consecutively. Bloomberg announced his campaign only 86 days ago.

The wizard behind the curtain of all that paid media, however, has been far less visible to the public. By passing on the competitions in Iowa and New Hampshire, and the first year of televised town halls and interest group cattle calls, Bloomberg has not needed to flex the improvisational campaign muscles his rivals have been building for months.

His in-person campaign approach has also been outsourced to a massive field operation that employs about 1,700 people in 43 states. They have proved adept at attracting crowds for him of about 1,000 as he jets around the country for events with free food and wine, live music and complimentary campaign T-shirts.

Bloomberg’s actual performance on the stump can be underwhelming by comparison, as he reads from teleprompters to deliver even a standard 15-minute speech after multiple introductions, and he regularly cuts short the time for glad-handing with the public afterward.

Bloomberg is the first candidate to make the Democratic debate stage this cycle without meeting any fundraising goals, after a change last month by Democratic National Committee Chairman Tom Perez allowed candidates to qualify for the debate either by winning at least one delegate or by scoring 10 percent or more in four qualifying polls.

The poll that put Bloomberg onstage, from NPR-PBS NewsHour-Marist, showed him with the support of 19 percent of Democratic primary voters nationwide — in second place behind Sanders, who received 31 percent. The poll, published Tuesday, was conducted between Feb. 13 and 16.

The debate will air Wednesday on MSNBC and NBC at 9 p.m. Eastern. Candidates who qualified either with polling or by winning national delegates in Iowa or New Hampshire include Bloomberg, Biden, Warren, Sanders, Klobuchar and Buttigieg.

Bloomberg has prepared for the sparring by shifting his policy proposals to more closely align with the appetites of Democratic primary voters. He has proposed a modest financial-transaction tax that would hit many of the subscribers to his company’s financial-data terminals, and a tax increase for those like himself in higher tax brackets. He has called for racially targeted programs to increase black homeownership, double the number of black-owned businesses and increase the net worth of black families. He has also repeatedly apologized for stop-and-frisk policing.

If anything, Bloomberg has tried to use his wealth and emotional distance from political combat as a selling point. The central message of his campaign is that he has the ability and record to defeat Trump and the managerial competence to improve the lives of voters. While his rivals attack his wealth as obscene and his spending as profligate, he has embraced the same as the appeal of his candidacy.

“There is nothing Trump can do or say that can hurt me,” Bloomberg said last week in his stump speech in Chattanooga, Tenn. “I won’t let him bully you, either.”