Mark-Viverito, whose political positions are largely to the left of the famously liberal Mayor Bill de Blasio, is becoming a prominent voice -- and Twitter pundit -- on such issues as immigration and criminal justice reform.

She wore an "I Can't Breathe" T-shirt in honor of Eric Garner's last words after he was placed in a fatal police chokehold. She called out Gov. Andrew Cuomo, the most powerful Democrat in the state, for his stances on charter schools and his lack of public statement on a gas explosion in East Harlem. And she will travel this month to Arizona, a hotbed of immigration debate, to push for a municipal identification card that primarily benefits immigrants who entered the country illegally.

"I believe in equality and justice for vulnerable populations," Mark-Viverito told The Associated Press in an interview this week. "I want to be part of that conversation. I want to be part of moving the dial."

Mark-Viverito, who was born in Puerto Rico, spent years as an activist and labor organizer before being elected to City Council in 2005. After securing re-election in 2013, she made a bid for the speaker post, a job traditionally doled out by the Democratic party's borough bosses.

But de Blasio took the unusual step of intervening in the council's race to elect a new speaker, throwing his support behind Mark-Viverito -- a longtime ally and one of the first to endorse his longshot campaign -- and pressuring council members to do the same.

Mark-Viverito won, becoming the first Hispanic to hold the powerful post.

With a City Council comprised of 48 Democrats and just three Republicans, the body helped usher in de Blasio's vision of an activist, liberal government. In rapid succession, the council passed an expansion of paid sick leave and living wage reform, opening up the speaker to criticism that she was indebted to de Blasio and would march lockstep with him.

"She was an obscure local councilwoman who got catapulted into a very visible role that she was not immediately prepared to leverage," said Dan Gerstein, a New York political strategist. "It was inevitable that it would take her some time to find her footing."

But there have been clashes. Most notably, the council championed hiring 1,000 new police officers during the last budget season, only to be turned down by the mayor's office. But Mark-Viverito has continued to advocate for it, and the mayor's office appears set to blink this year and at least hire some officers.

Mark-Viverito sees no conflict between her stance to hire more officers and her previous criticism of the police force. When she wore the Garner-themed shirt, she drew the wrath of the police unions, which, during their conflict with City Hall over the winter, demanded that de Blasio denounce Mark-Viverito.

 He did not. And she won't apologize.

"When it comes to issues of fairness, of sticking up for the dispossessed, she will not compromise," said City Councilman Corey Johnson. "She has strong beliefs, she won't back down."

Some of her bold stances may be fueled by the knowledge that term limits will force her out of office after 2017. She has moved past de Blasio on some calls for criminal justice reform, including the creation of a bail fund for minor offenders and a call for some low-level violations, such as jumping a subway turnstile, to warrant only summonses instead of jail time.

But immigration is the issue on which her profile is largest. She's become a semi-regular on cable TV news as the debate in Washington heats up, and the council has established a fund for unaccompanied immigrant minor's legal fees.

The municipal ID card is likely her signature achievement. As of last week, more than 100,000 New Yorkers have signed up for the card, which will allow undocumented immigrants -- and other groups such as the elderly and the transgendered -- to access vital city services.

"I don't believe you should be criminalizing anybody who has an intention to come here because they want to provide for their families and don't see any other means to do it," she said.

Mark-Viverito, 45, is a private person, rarely discussing her life outside City Hall. And unlike her predecessor as speaker, fellow Democrat Christine Quinn, who ran for mayor in 2013, Mark-Viverito has mostly kept her political ambitions to herself (although she has said she would not pursue Rep. Charlie Rangel's seat when he retires in 2017).

That caginess is why her outspoken, and at-times goofy, frequent Twitter usage has come as a surprise to so many.

She runs her own account, rarely running Tweets by her staff, including when she criticized Cuomo last year. She also used Twitter to reveal that she has human papillomavirus, or HPV, and used the moment to urge New Yorkers to get vaccinated.

But Twitter is also where she displays her lighter side. She live-tweeted the Grammys, has used it to tease reporters and, the night of her April 1 birthday, she posted a photo of a diamond ring with the hashtags #OMG #YES, sending reporters -- and some of her staff -- scrambling.

Eleven minutes later, she sent another tweet: #HappyAprilFoolsDay.

Source: Associated Press