The Rev. Al Sharpton has never had a friend in the mayor's office like Bill de Blasio.

The Harlem-based preacher is enjoying his closest access to the seat of power since he came of age as an activist during the Ed Koch era.

"There's always an open line of communication. Always," said Rachel Noerdlinger, a top Sharpton aide for 14 years who is now first lady Chirlane McCray's chief of staff. "We didn't have that before: access . . . There hasn't been a thing that we have asked Mayor de Blasio to do that he hasn't done."

Sharpton, 59, and de Blasio, 52 -- the first Democrat to occupy City Hall in 20 years -- are politically simpatico. But their bond also reflects easing racial tensions in the city and Sharpton's evolution from his polarizing past.

Sharpton's National Action Network has met with the new Department of Investigations commissioner, Mark Peters. Sharpton gave his blessing to and met with Police Commissioner Bill Bratton, who Sharpton said wouldn't meet him as NYPD head in the '90s.

Sharpton and de Blasio have each other's backs. De Blasio last week praised Sharpton as a good citizen amid new disclosures over his FBI informant past. Sharpton in February ridiculed attacks on the mayor for calling the NYPD about Bishop Orlando Findlayter, a de Blasio ally arrested after a traffic stop on warrants.

They have made almost a dozen public appearances together since de Blasio's election. They talk regularly by phone about politics, said Noerdlinger. They also talk about McCray, whose career Sharpton has followed for years.

"We both value his advice and his guidance," de Blasio said while appearing at a NAN convention Wednesday.

That's not how it used to be for Sharpton at City Hall. Koch wouldn't have anything to do with Sharpton. David Dinkins, the city's first black mayor, was a friend but kept his distance publicly. Rudy Giuliani was fiercely adversarial toward him.

Michael Bloomberg enjoyed a cordial "relationship of convenience" with Sharpton, said Christina Greer, Fordham University assistant professor of political science. But they fought over Sharpton's demands to end perceived racial profiling in the NYPD's stop-and-frisk practices -- a change de Blasio also advocated.

In the late '80s and '90s, Sharpton was a lead player in racially charged controversies, including advising Tawana Brawley, a black teen found to have falsely accused a group of white men of rape. The latter-day Sharpton, Dinkins said, has grown from "rabble-rouser" to "eminently more responsible."

"I think especially today, he would be somebody who is concerned with fairness and justice irrespective of race and ethnicity," Dinkins said. "That may not have always been the case with him."

His gig as an MSNBC host gives Sharpton a daily national platform. Last week's NAN convention drew not only de Blasio but President Barack Obama and U.S. Attorney General Eric Holder.

Not everyone sees the Sharpton-de Blasio alliance as a plus for the city. State GOP chairman Ed Cox said, "Al Sharpton and Bill de Blasio deserve each other: Both are political showmen whose divisive shticks lack constructive substance."

Still, the ranks of Sharpton's enemies have thinned over time. Former Gov. David Paterson joked in an interview that politicians who were once Sharpton's most merciless critics "would push me out of the way to get a better seat" at NAN rallies now.

Asked last week how he views himself then and now, Sharpton said, "I've grown. I've learned to do things differently. But I do not have any difference today in my calling on the government to do what is right."