Whether he will actually demonstrate any grace on that stage is one of the biggest questions to date.
Bloomberg has risen to second place in a new national poll and appears well-positioned for Super Tuesday in two weeks. He has gotten to that point by essentially carpet-bombing the country with hundreds of millions of dollars in ad spending, while the other candidates have focused on the first four states, where Bloomberg isn't on the ballot.
The combined effect: He's had a pretty free ride, with the scrutiny beginning in earnest only in recent days. He's largely avoided unpredictable and impromptu moments, including talking to reporters and voters.
Tonight is when that changes in a major way. Sen. Bernie Sanders, I-Vt., may be the leading candidate in the race, but it seems likely to be the debutant who will garner the most attention and attacks. And there's more than enough to work with. Bloomberg's comments about women and minorities and crime have circulated heavily in recent days, and he'll have to answer for them on the spot. He's also a relatively recent convert to the Democratic Party, which has moved against billionaires such as him in recent years.
How will he handle it? Unfortunately with Bloomberg, we don't have a good, recent debate performance to draw upon. The last time he debated was in 2009, when he faced off twice with New York City comptroller Bill Thompson. Thompson at the time was waging an uphill campaign as the Democratic nominee against the two-term incumbent mayor, who was then running as an independent.
But there are some lessons to glean. A few observations:
• Bloomberg does his homework
Stories have been written about the extensive preparation underway for this big moment in Bloomberg's campaign. It has been underway for weeks, even though it wasn't totally clear Bloomberg would qualify for tonight's debate, and top aides have been playing the roles of his Democratic opponents.
Bloomberg's twin clashes with Thompson show that he's rarely caught off-guard. He entered the latter contest a week before the election with a relatively safe double-digit lead in the polls, but he was arguably the more combative candidate, and he was generally viewed as the winner. He repeatedly pointed to Thompson's time as head of the city's board of education in the 1990s and also to Thompson having failed to raise concerns about the mayor during his time as comptroller under Bloomberg.
"Comptroller Thompson was the comptroller for the last eight years, and if there was all this waste, it's a shame he didn't point it out back then," Bloomberg said.
He added at another point: "You can't have it both ways. Bill has for eight years in a row said that our plans, our financial plans every time he's testified were prudent, well thought-out and appropriate. Now all of a sudden he's running for mayor, and he wants to disavow that."
When Thompson claimed that he set up the city's schools to be taken over by the mayor's office early in Bloomberg's tenure, Bloomberg - as he did often in the debate - turned it around.
"Well, you did pave the way for mayoral control," Bloomberg said. "Everybody looked at the job that was done in the 1990s, when you ran the board of education, and they said, 'No mÃ¡s!' "
• The charisma and empathy question Even as that last line worked - and drew rare applause from the studio audience - it wasn't exactly delivered with aplomb. Bloomberg's style is almost completely charisma-free, and his visage practically screams "technocrat." He makes odd gestures with his hands, doesn't look particularly thrilled to be there and occasionally stumbles over his words.
Toward the end of the last debate with Thompson, the two candidates were asked to grade each other for their performances in their jobs. Thompson said he would be generous and give Bloomberg a D-minus. Bloomberg, responding second and with plenty of time to think about a dicey question, tried to joke that Thompson was the best comptroller he had worked with. The punchline was supposed to be that Thompson was the only comptroller Bloomberg worked with, but it just didn't land.
In another key moment, Bloomberg was asked to define what it was to be middle class in New York City. He talked generally about what kind of lifestyle it was rather than how much money such people made, but it didn't exactly scream "empathy."
"They set the alarm clock, and they punch the time clock, and they're proud of being New Yorkers and proud of working in the diverse society that we have," Bloomberg said.
Pressed for numbers, Bloomberg again demurred.
"There isn't a number because someone who lives here who is single lives very differently from someone with family," Bloomberg said, ignoring that this is usually factored into definitions of middle class. "A middle-class person is a person who has a job and can pay the bills but does not have a lot of extra money and probably has a little bit of fear of what would happen to them if they lost their job."
• A prickly side
That empathy gap also came up when Bloomberg was asked about his wealth quadrupling during his time as mayor.
Bloomberg pretended not to know whether that was true - which is a little difficult to swallow - and then bristled at a follow-up question about whether his wealth made him out of touch.
"What do you think when you hear that criticism?" the moderator asked.
"Me? Which criticism?" Bloomberg asked, apparently genuinely not understanding the line of questioning or that it was for him.
Then, though, Bloomberg shook his head and demonstrably shrugged, as if he didn't appreciate being asked about it. It was the kind of thing people around Bloomberg point to when they express concern about his prickliness possibly leading to a bad moment tonight.
Bloomberg arguably rescued the moment, though, by turning the question from empathy to competence.
"It's very easy to say, 'I feel your pain.' That's not what we need," Bloomberg said. "We need people who are going to go and actually do things to make things better."
Watching it, it was easy to see Bloomberg making a similar argument tonight: I may be a stiff, very New York billionaire and not exactly your ideal, but we need someone who can beat President Donald Trump.
Whether that will be the prevailing image he projects tonight - when he'll face candidates more skilled and practiced than Thompson, and with fire coming from all sides - will be key. And it'll go a long way toward determining whether Bloomberg is a contender or just a rich guy who purchased a polling bubble that will soon burst.
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