Picking a favorite bagel on National Bagel Day is bound to get any New York City mayor into trouble with some portion of his 8 million constituents, who are bound to have differing hard-held opinions.

But Bill de Blasio, following a failed presidential campaign, managed to cause a particularly unusual uproar.

In a Twitter post on Wednesday, Mr. de Blasio declared his love for a bagel that fits his political persona: the Bagel Hole bakery in Park Slope, Brooklyn, which serves a chewy and celebrated variety in the leafy neighborhood where the mayor raised his family.

Then he crossed into treacherous territory for bagel aficionados: He said his go-to bagel was whole wheat with extra cream cheese. Toasted.