NEW YORK Halfway between Third and Lexington Avenues on 101st Street, just on the border between the posh Upper East side of Manhattan and the Southernmost part of Spanish Harlem a group of about a hundred people are waiting for the Rev. Jesse L. Jackson.

On one side of the street stands a row of apartment buildings five stories high, which were built around the turn of the century. On the other side stands a similar row, but this one shows the scars and charred brick of a recent fire. The building has been ravaged by vandals, like hundreds of others in this area.

Three blocks away about a thousand marchers have been waiting for an hour and half for Jackson to show up. But the civil rights leader and Democratic Presidential candidate has decided to hold a hastily-scheduled press conference to protest the fact that the families who lived in the burned-down building have not been placed in permanent housing by the city government.

This is the sort of media event the Jackson campaign has thrived on in its effort to capture votes from the so-called Rainbow Coalition of women and minorities.

The minority vote is expected to be key in tomorrow's super-charged New York primary, which will award 252 delegates to the July Democratic convention, the biggest single block of delegates yet. Thirty-three additional uncommitted delegates will be chosen later by Democratic officials here.

Fifteen percent of the state's 3.5 million registered Democrats are Black, and voter registration drives have added more than 200,000 minority voters to Democratic rolls in the past year.

"These are our people, I've never seen so much enthusiasm," says William Lynch, Jackson's New York campaign manager.

Lynch, discounting polls which put Jackson, with 21 percent, in third place behind former Vice President Walter F. Mondale, with 41 percent, and Sen. Gary W. Hart (D-Colo.) with 28 percent, says he thinks Jackson can win.

"I don't think the pollsters get to our people--the minorities," he says.

When Jackson finally arrives at 101st Street, the crowd has swelled to about 200, and the candidate stands in the doorway of one of the buildings, holding the hands of children form the neighborhood.

"We must train our youth to end slums and rebuild America." Jackson shouts in his deep preacher's cadence.

Carmen Rios, a mother of two who says she is an welfare and lived in the building that burned down, says that she thinks Jackson is the only candidate "who really cares about poor people. He offers me hope."

Buoyed by a strong showing in the recent Illinois primary and on the televised debate between the candidate last week, Jackson is heavily favored to win a lion's share of the minority vote tomorrow. But various packets of New York City's Black and Hispanic community are still up for grabs.

Harlern, in fact, is the base of a number of Black politicians, including Rep. Charles B. Rangel (D.N.Y.), who support Mondale, Jackson's assured support in the Black community is centered in Brooklyn, where a new younger generation of politicians is developing.

The division between the new and older generations of Black political strength is demonstrated by the decision of the New Amsterdam News, a prominent Black weekly, not to make an endorsement.