On Thursday night, The New York Times reported that former New York City mayor Michael Bloomberg was on the cusp of running for president, taking preliminary steps to register in the Alabama primary. It is uncertain whether Bloomberg will go through with this move. He’s flirted with the presidency before, notably in 2016 when he expressed concern that Bernie Sanders would be the Democratic nominee. But Bloomberg has always gotten cold feet.

If Bloomberg does join the fray, the Democratic race will be top-heavy with both billionaires and anti-billionaires. Bernie Sanders and Elizabeth Warren are running populist campaigns built on the promise of taxing the ultrarich. Bloomberg will be the second billionaire running to be the Democratic presidential nominee, joining former hedge fund executive Tom Steyer. Former Maryland representative John Delaney isn’t quite in the same league—but he still has a fortune that can’t be easily sneezed at of a quarter-billion dollars.

Possibly reacting to the news of Bloomberg’s entry into the race, Sanders tweeted, “The billionaire class is scared and they should be scared.” One way the billionaire class is reacting to what they see as threats is by becoming more politically active. There are only 700 billionaires in the United States, roughly 0.0002 percent of the population. If we include Bloomberg, then two of the 18 Democrats running for president are billionaires, 11 percent of the total.

This blight of billionaires and near-billionaires illuminates the class war inside the Democratic party. While Steyer is running as an unconventional outsider candidate, both Delaney and Bloomberg style themselves as centrists resistant to calls for economic justice and higher taxes on the wealthy.

Bloomberg’s actions illustrate the problem with even the most progressive billionaire. It’s easy enough for leftists to criticize the likes of the Charles Koch or Mercer families, who generally spend their fortunes bolstering reactionary causes. Bloomberg, by contrast, is supposed to be one of the good billionaires. He, like Steyer, gives money to combat climate change. Bloomberg has also taken the issue of gun control to heart.

But there are limits to Bloomberg’s benevolence beyond his resistance to paying more taxes. As mayor of New York, he took a hard line on criminal justice issues, blocking efforts to end stop-and-frisk. He has a dubious record on gender issues. As Gawker noted in 2016, “Bloomberg is, according to many, many accounts, a crass sexist, and his company, Bloomberg L.P., has a lengthy history of alleged gender discrimination.” More recently Bloomberg has been skeptical of the #metoo movement and expressed doubt about sexual assault allegations against journalist Charlie Rose, even though they were made by multiple women and cost Rose his job at CBS news.

The problem with Bloomberg is not just that he’s a mixed bag politically, but also the arrogance in thinking that his presidential run is needed. According to The New York Times, Bloomberg entered the race because he has “grown skeptical that Mr. Biden is on track to win the Democratic nomination and he does not see the two leading liberals in the race, Senators Elizabeth Warren of Massachusetts and Bernie Sanders of Vermont, as strong candidates for the general election.” Bloomberg is not wrong about Biden, a vulnerable front-runner whose campaign keeps going only by inertia. Although he’s unlikely to have read it, Bloomberg is echoing the logic of the recent anti-endorsement published by The Nation.

But even if we stipulate, for the sake of argument, that his assessment of the top three is accurate, it still doesn’t explain why Bloomberg needs to run. After all, it’s not like the Democratic field is bereft of candidates who broadly share Bloomberg’s centrist politics. The centrist lane includes Joe Biden, Michael Bennet, Cory Booker, Steve Bullock, Pete Buttigieg, John Delaney, Kamala Harris, Amy Klobuchar, and Joe Sestak. With Bloomberg in the mix, there are now 10 candidates all competing for the same fraction of the Democratic Party.

Even from Bloomberg’s own point of view, what he is doing is counterproductive. Given the makeup of the race, he’s most likely to hurt the leading centrists, Biden and Buttigieg, making it more likely the race will be won by Sanders or Warren. The most sensible path for Bloomberg would to pick a centrist candidate and set up a super PAC to support him or her. Alternatively, if Bloomberg is worried about Trump’s reelection, he could buy ads attacking Trump in swing states.

The fact that Bloomberg is on the verge of running a vanity campaign rather than pursuing these more sensible options is certainly proof of a healthy ego. But it also highlights a deeper problem. Aside from whatever personal gratification Bloomberg gets from fantasizing about being president, he’s also part of a larger trend of billionaires becoming more politically vocal in defense of their class interest.

On Monday billionaire investor Leon Cooperman actually cried during an appearance on CNBC’s Halftime Report while describing the trauma inflicted on him by Warren. “I don’t need Elizabeth Warren telling me that I’m a deadbeat and that billionaires are deadbeats,” Cooperman said as he struggled to hold back tears. On Wednesday, Microsoft founder Bill Gates expressed concern that under Warren’s tax plan he would end up with a tax bill of $100 billion (a worry that is only true if he lives a very long life, since the tax rate would be 6 percent on a fortune of more than $100 billion). He also hedged on answering if he would support Warren over Trump.

Both Cooperman and Gates are typically classed among the good billionaires since they give extensively to charity. But they also illustrate the problem with even the most liberal billionaire. As Cooperman explained, “She’s screwing around with the wrong guy. I want to give it all away, but I want to control the decision.”

The question of “control” explains the fundamental division between philanthropy and social democracy. Billionaires like Bloomberg, Cooperman, and Gates can be quite generous in giving away money—so long as they continue to control the purse strings. That type of charity, even for the best of causes, only reinforces their power in society. But social democracy isn’t about charity but rather bringing wealth, which is socially created, under democratic control. Taxing wealth and reallocating it as a democratic government sees fit is crucial to creating a society where power is more evenly distributed. Charity is commendable in many ways, but it doesn’t alter power relations.

Sanders and Warren are pursuing a hard path. To democratize the American economy, they’ll need to not just fight traditional Republican foes but also alienate some erstwhile allies. Among the former friends that need to be shunted aside are the good billionaires.