Dan Janison Melville. N.Y. Tuesday January 26, 2010. Daniel Janison,

Dan Janison has been a reporter at Newsday since 1997.

New York City voters knew before they elected Mayor Bill de Blasio that his resume was long on messaging and short on managing.

So it is worth noting that the next 100 days will say more about de Blasio's ability to command a massive organization for the first time than did the first 100 days, which he marks Thursday.

With a crucial Albany budget settled, attention swings to the workings of de Blasio's City Hall. He must try to negotiate an unprecedented backlog of expired labor contracts, settle a tight budget and mobilize a massive new prekindergarten program -- all while reacting to any unforeseen emergencies from atop a chain of command that still has holes to fill.

Predicting de Blasio's chance of success in the second 100 days becomes especially tricky in light of the unique blend of advances and stumbles of the first.

Insiders say he can draw lessons from his missteps.

A recent reversal on charter schools may prod him to better size up his policy foes. A tempest over his NYPD drivers caught on camera running stop signs offers a symbolic message about the hazards of double standards, even if unintended. Early glitches in snow removal might serve as a reminder that he's judged by mundane events on the street.

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With the latest Siena College poll showing not quite half of city voters approve of his job performance, continued talk of an electoral "mandate" could ring hollow.

"His problem is not a long-term message problem. It's the day to day," said a former city staffer who knew de Blasio in the City Council. "As for the polls, he seems to have mistakenly thought he had a mandate, when [he won because] he was really the least offensive guy in a totally offensive field of candidates."

But looking ahead, "There's plenty of time to turn things around. The guy is talented."

De Blasio, who will address the coming months in a speech at the Cooper Union Thursday, has proved willing to push big policy commitments. As promised, he resolved a federal lawsuit involving police stops, signed a measure assuring private employees sick days and thrust pre-K programs into the spotlight in the state budget fight this year, even if he failed to get the tax he wanted to fund it. The administration also quickly wrested affordable-housing concessions from developers of projects in Brooklyn and on Manhattan's West Side.

For someone who had the mayoralty all but locked up by last September, his appointment of agency heads proved relatively slow. After 100 days, he still has some Bloomberg administration holdovers in place.

De Blasio backers insist the plodding pace reflected a desire to get it right. Calling the appointments "high-caliber," ex-White House aide Harold Ickes, who served on the mayor's transition team, said: "Achieving . . . considerable diversity is not always easily done. And we all know how hard it is to find the right person for the right job."

De Blasio's chronic lateness for scheduled events has jelled into a fixed caricature. On Opening Day at Citi Field, with de Blasio throwing out the ceremonial first pitch, Mets first baseman Ike Davis was delayed taking his position. "Usually, it's de Blasio who's always late," quipped a Mets TV announcer, to laughter in the booth. "Maybe Ike was counting on de Blasio being late."

If he is relaxed about punctuality, his government better not be. To expand pre-K by 20,000 pupils in September, it must prepare new space, hire trained educators, handle applications and coordinate education programs -- a complex project. Some school-system insiders wonder aloud how much will really be done on time.

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For the city budget due June 30, de Blasio should have a strong hand to play. In January, he backed the candidacy of new City Council Speaker Melissa Mark-Viverito (D-Manhattan), and she's now his fiscal negotiating partner.

But a budget involves labor costs, and union talks face a long road. "It's going to be hard for all sides," said a longtime union operative. "And that's not because in this instance either side is obstinate or adamant. From what I hear, both sides sound committed to being creative and trying to figure something out."

Thousands of gnarly details loom -- as they do with all the rookie mayor's challenges.