But Bloomberg has not been without other local endorsement options—just not for mayor. Earlier this week, hizzoner’s spokesman said that Bloomberg would endorse Newark Mayor Cory Booker in his bid to win New Jersey’s U.S. senate seat later this month. (The date of the special election is October 16^th.) The New York Times has reported that Bloomberg’s PAC will spend $1 million on ads to boost Democrat Booker in his surprisingly close race against Tea Party Republican Steve Lonegan. The most recent poll, from Quinnipiac, shows Booker leading Lonegan by 12 points—the same margin as last month, but down considerably from pre-September polls that showed Booker on top by more than 20 points.

More divides Booker from de Blasio than their diverging electoral fortunes (though Booker, like de Blasio, is still favored to win) or their backing, or lack thereof, from Bloomberg, or, for that matter, the Hudson River. Each personifies a distinct future for the Democratic Party—futures that ultimately are mutually exclusive. As Washington marvels at the degree of Democratic unity and Republican disarray at the national level, it’s easy to overlook the intra-party differences that still split the Democrats, particularly at the municipal level. A look at Booker and de Blasio can illuminate some of the Democrats’ emerging fault lines.

To be sure, the Democrats no longer suffer from significant internal differences on social issues or foreign policy. When it comes to promoting gay rights, reproductive freedom and immigrant legalization, the party is effectively unified. On foreign and military policy, there is widespread relief that America’s overseas interventions are winding down and a widespread wish that they not be wound up. It’s only on certain economic issues that the Democrats are divided. Just some issues: Almost all party leaders support making taxes more progressive, raising the minimum wage, investing more in infrastructure, extending health coverage through Obamacare (and beyond Obamacare where possible), and making education more affordable. But at the state and, even more, the municipal level, there are serious differences over the role of unions, the future of public education, and the corporate-backed privatization of services. De Blasio and Booker diverge on issues of substance here, and have come to symbolize even more disparate paths. As much as they differ on the words that will shape the party’s future, they differ even more on the music.

Not to put too fine a point on it, Booker is a corporate Democrat and de Blasio an anti-corporate Democrat. Booker sees the corporate and financial sectors as allies in helping America’s poor, while de Blasio sees the corporate and financial sectors as the groups that have used their power to rig the economy in their favor and at everyone else’s expense.

Given both his city’s and his own dependence on the kindness of the rich, it was nonetheless stunning but in no way surprising when Booker told viewers of Meet The Press, in the midst of the Obama re-election campaign’s attacks on Mitt Romney and Bain Capital, that he found such attacks “nauseating.” “Enough is enough,” Booker said.  “Stop attacking private equity.” Booker’s vision of the forces for progressive social change apparently includes the very poor and the very rich—the former as beneficiaries, the latter as dispensaries, of private wealth. Any mayor of a city like Newark is surely entitled to periodically adhere to the adage that beggars can’t be choosers, but at a time when the financial sector has brought the broader economy to ruin, when profits have soared due in large part to the suppression of wages, and when the continual upward redistribution of income has battered the middle class, Booker’s comments—and the sensibility they betrayed—could not have been more at odds with that of his party. Particularly with that part of the party that de Blasio has come to personify.

After running fourth for many months among the candidates in New York’s Democratic mayoral primary, de Blasio surged to the top by campaigning, essentially, against the very economic trends on which Booker seemed to rely. New York, de Blasio said repeatedly, had become a tale of two cities—a Bloombergian, more benevolent version of Fritz Lang’s Metropolis, where nearly half the residents lived in or near poverty while the super-rich swanned about as never before. Long identified with the Working Families Party, de Blasio championed the city’s union workers and excoriated Bloomberg and the mayoral candidate closest to him, City Council President Christine Quinn, for blocking passage for three years of a paid-sick-leave ordinance he supported. He campaigned as well against the stop-and-frisk-minority-young-men policy of the New York police, which Bloomberg fervently backed, and made clear that the city’s current policy of letting charter schools set up shop rent free in city-owned facilities may well be discontinued. He’s called repeatedly for higher taxes on the rich, though that’s a change that would have to be enacted not in council chambers but by the legislature in Albany—and then pass muster with Governor Andrew Cuomo. And to date, Cuomo has been more a Bookeresque friend of the rich than a de Blasian populist.

For Booker and de Blasio merely personify in the extreme the two main tendencies in today’s Democratic Party. Chicago Mayor Rahm Emanuel and, at times, former Los Angeles Mayor Antonio Villaraigosa, have also exemplified a breed of Democratic officials, chiefly mayors, who sought and cultivated corporate allies in their efforts to privatize services and oppose public-sector unions. Cuomo was one of a smaller group of Democratic executives who have been cool to the idea of raising taxes on the rich. On the other side of the Democratic divide, Senators Elizabeth Warren, Sherrod Brown, and Jeff Merkley are just some of the party leaders who have demanded far stricter regulations on finance and legislation to strengthen the rights and interests of workers. These Democrats tap into the increasingly strong economic egalitarianism of the party’s activist base—an egalitarianism that has provided the foundation for de Blasio’s remarkable surge.

A handful of Democrats are managing to work on both sides of the party’s dividing line. California Governor Jerry Brown steered to passage a ballot measure that raised taxes on the rich to balance the state’s budget and successfully backed a legislative hike in the state’s minimum wage to $10-an-hour. He also signed into law a number of bills that the state’s business organizations had been backing—though none so fundamental as the hike in the minimum wage—and discouraged the Democratic-dominated legislature from enacting more tax hikes atop those that the voters authorized.

Perhaps the largest question for Democrats is how the party’s presumptive presidential nominee will respond to this rift. If Hillary Clinton continues to take counsel from her family’s retinue of economic retainers—Robert Rubin and his many protégés—that would signal a continuation of Bill-Clintonomics, with its bias towards finance and pro-corporate free trade, and, as inadequate counterweights to the unegalitarian consequences of that bias, support for a more generous earned income tax credit and a more progressive tax code. To connect with that new generation of Democratic activists, however, Hillary Clinton would need a new generation of advisers who’d recommend policies that would more forcefully take on America’s plutocratic order. More de Blasio, less Booker. Therein lies the Democratic future—if that future is to last.