Public Advocate Bill de Blasio may have some good ideas as he carves out a leading role among the city's Democratic mayoral candidates -- but his misleading and divisive "tale of two cities" scenario isn't one of them. The story line goes like this:

While 400,000 millionaires call New York City home, nearly half our neighbors live near the poverty line. The middle class isn't just shrinking, de Blasio says, it's in danger of disappearing. "That's not the kind of New York I want to live in," he declares. Us either.

But what does a dangerously shrinking middle class have to do with the millionaires who live among us?

De Blasio thinks we could hit up these big-time earners -- and also those who make more than $500,000 a year -- with a new tax hike to pay for universal prekindergarten.

Still, what sense does it make to sell this program with a destructive and deceptive us-against-them pitch?

In a town famous for its ghastly tax burdens, the city's Independent Budget Office confirms that New York's 1 percenters account for more than 43 percent of the city's income-tax revenues. This population also happens to be highly mobile -- meaning most of them live in New York because they like it. That could change quickly with a mayor who sets out to make them villains.

The next mayor will face a huge challenge as he or she tries to manage a city where the middle class is reeling as the Great Recession winds down, where the cost of living is higher than anyplace else in the country -- and where a third of the population pays precisely no New York City income tax because its wages are too low.

Citywide programs to stimulate affordable housing are urgently needed as average rents hit $3,100 a month in the four boroughs excluding Staten Island. The next mayor must noisily force the New York City Housing Authority to clear up an outrageous backlog in apartment repairs.

The next mayor must also twist arms and persuade the state's MTA board to stop the rapid escalation of city bus and subway fares. These are all effective ways to rescue an embattled middle class. Yelling at the rich is not.