Michael Appleton, Associated Press
New York City Mayor Bill de Blasio and Senator Charles E. Schumer, Democrat of New York, take a photo with commuter Zilla Kasimov as they ride the R subway train from Brooklyn to City Hall in Manhattan during morning rush hour on Thursday, April 9, 2015.

NEW YORK — New York City Mayor Bill de Blasio has deep ties to Bill and Hillary Rodham Clinton.

That's why so many eyebrows were raised in political circles when he declined to immediately endorse her for president during an appearance Sunday on "Meet the Press."

He said he needed to see Clinton's "actual vision" and "substance" before offering his blessing.

The backlash was immediate.

Several Clinton allies and the front pages of the New York City tabloids chided him for appearing disloyal and for creating a distraction.

But some pundits have suggested that he'll increase the value of his endorsement if he waits.

De Blasio is trying to bolster his national profile as a leading voice on liberal issues. He's said he wants to move Democratic candidates to the left.