CITY HALL — When Mayor Michael Bloomberg wanted to enter the national debate on issues ranging from gun violence to the environment, the billionaire entrepreneur opened up his checkbook and made an immediate impact.
While still mayor in 2011, Bloomberg donated $2.5 million to the Mayors Against Illegal Guns Action Fund, a group he founded with then Boston Mayor Thomas Menino. The same year, he gave $50 million to the Sierra Club to help shut down coal-fired power plants.
So when de Blasio declined to endorse his former boss Hillary Clinton on the day she announced her campaign for president because he wanted to see her "vision," observers say he was using one of the tools at his disposal to insert himself into the national debate.
"De Blasio is trying to enhance his reputation as the leader of the left by stealing a bit of the spotlight," said Kenneth Sherrill, professor emeritus of political science at Hunter College.
"He now has people talking about him who wouldn't otherwise be talking about him and he will now have more people paying attention when he does endorse."
De Blasio's spotlight-stealing moment coincides with the launch of a national push to focus on income inequality for the 2016 presidential elections.
Two weeks ago, de Blasio was called a "national hero" among progressives by activist Van Jones when he launched an effort to create a document similar to the Republican Contract With America from the 1990s.
The mayor said the group will hold a presidential forum after laying out an agenda to tackle income inequality.
Last week de Blasio embarked on a Midwest trip to Nebraska and Iowa to discuss what he called the "economic crisis of our time."
De Blasio won election as mayor with "A Tale of Two Cities" campaign theme and focused on issues such as income inequality and discriminatory policing.
During his first 16 months in office, the mayor has secured universal pre-K, raised the minimum wage on city-funded projects and is fighting to increase the minimum wage.
Deepak Bhargava, executive director of the Center for Community Change and a member of de Blasio's progressive coalition, said those policy victories give the mayor the stature he needs to take those issues to an audience outside New York City.
"His passion for the issue and track record of delivering in New York City uniquely position him to help galvanize progressive forces to ensure that candidates propose big solutions that are equal to the scope of the problem," Bhargava said.
Yet de Blasio, who ran Clinton's successful 2000 campaign for U.S. Senate, was criticized for the vagueness of saying he wanted to see a "progressive vision" from the former secretary of state.
Democratic strategist Hilary Rosen said Clinton was fighting for middle class and poor families before de Blasio "could even articulate any vision at all."
Former Rep. Anthony Weiner, whose wife Huma Abedin is a top Clinton aide, also criticized de Blasio.
“This notion that he is somehow this spokesperson for some wing of the party that Hillary needs to audition for, I think, is wrong and not helpful,” Weiner, who ran against de Blasio for mayor in 2013, told the Wall Street Journal.
During his Midwest swing, de Blasio laid out more specifics about the type of vision he'd like to see, detailing three key principles and an eight-point agenda to address income inequality.
It included changing the tax code so that wealthy Americans pay more, raising the minimum wage to keep pace with the cost of living, passing national paid sick leave legislation and making pre-K available to all children in this country.
On Thursday, de Blasio gave another speech on income inequality at Drake University in Des Moines, Iowa, where he criticized politicians on both sides of the aisle for not doing enough to address income inequality.
It's not the first time de Blasio has tried to tackle the issue. After Democrats lost control of the U.S. House of Representatives in midterm elections, the mayor said it was because they didn't address progressive issues. The mayor unsuccessfully tried to help Democrats win a majority in the state Senate to help further his own agenda.
Bhargava said de Blasio is "taking crucial leadership in helping to elevate issues of income inequality in the national debate" ahead of the 2016 presidential elections.
"The progressive community is united in wanting to see candidates of all parties propose big ideas on increasing wages, increasing the quality and availability of jobs and progressive taxation," Bhargava added.
Not everyone is pleased with the mayor's push for national prominence on income inequality.
State Sen. Diane Savino said she didn't have a problem with de Blasio being "a cheerleader for the Democratic party or the left wing of it" on Facebook Thursday.
"But, dude, you do have a city to run. If you want to go on a day trip, come to Staten Island and fill some potholes, come to Coney Island and help with youth violence, Brighton Beach needs its boardwalk back," she added.
Democratic consultant Donna Brazile said the dustup over de Blasio's refusal to immediately endorse Clinton was overblown.
"Secretary Clinton said she wants to earn the support of everyone," said Brazile. "What's the rush? It's not like the New York primary will happen soon."
Brazile said the flare-up will not damage the relationship de Blasio has with the Clintons, both of whom he has worked for.
"They are friends. And like most friends, all of this will be worked out in the future, not through the media," she said.