If there were any doubt, the prominent presence of the Rev. Al Sharpton at the groundbreaking of the Dr. Martin Luther King Jr. Memorial this week confirmed that Sharpton is more than just our hometown rabble-rouser. He's one of the most powerful civil rights leaders in America.

I admire Sharpton's ability to speak truth to power with eloquence and wit in the press, pulpit and even his presidential campaign.

But true leadership means more than protesting the symptoms of bad policy. It means using your power to change things for the better. That's why I'm disappointed that Sharpton hasn't done more to fight for real change when it comes to schools, jobs and financial justice right here in New York City.

Instead of going a mile wide, speaking nationally on everything from conservatives and the black church to the NFL's plans to introduce a cable football channel, Sharpton needs to go deep.

Consider the role that he could play on the Campaign for Fiscal Equity. He could throw his political weight behind getting our schoolkids, a third of them African-American, the billions in new funding that they're owed.

On the economic front lines, Sharpton could fight for policy to ensure that higher-quality jobs are created by the development projects he favors, like Atlantic Yards in Brooklyn. And he's been almost invisible on fights around the living wage, affordable tuition to CUNY and health care for big-box store employees.

We know that when this man cares about a cause, he can make change happen. After the shooting of Patrick Dorismond in 2000, Sharpton led a movement that drew attention to the misuse of force by the police. His actions had an impact.

He played a similarly critical role last spring when he quelled rising anti-immigrant sentiments among African-Americans - cautioning that it was "past time for all African-Americans to understand that our interests and those of immigrants are not at odds."

New York City needs more of that leadership, and too few are equipped to do it. But to be successful, Sharpton will have to lengthen his attention span, hold the elected officials he's endorsed accountable and lead by example.

That means no more deals like his gig as a spokesman for LoanMax, a company that specializes in offering short-term loans with up to 300% interest, provided people offer their cars as collateral.

These loans are a perfect example of predatory lending, which victimizes thousands of low-income New Yorkers. Sharpton told me he had been misled into thinking LoanMax was a new model. Regardless, he needs to be pushing for real industry reform - not doing commercials.

According to Sharpton, the city headquarters of his National Action Network will soon reopen - and he is newly committed to working on education, HIV/AIDS and poverty. He admits that "all of us have made mistakes" and says that "somebody has to take the risk of trying."

I hope he follows through. Dr. King became a hero because he was able to convert his hard-won popularity into lasting reforms. If Al Sharpton wants to truly pay tribute to that legacy, he will get away from the cameras and get to work.

Executive Director of the Drum Major Institute for Public Policy