It’s difficult to say what’s colder in New York these days – the winter weather or the frosty feud between the state’s two most prominent Democrat office holders.

New York City Mayor Bill de Blasio was sworn in for a second term on New Year’s Day, in a frigid 14-degree outdoor ceremony, with U.S. Sen. Bernie Sanders imported from Vermont to officiate.

Where was New York Gov. Andrew Cuomo? He was out on Long Island, swearing in a suburban county executive.

Odd couple

Though members of the same party, de Blasio and Cuomo have long been the Democrats’ odd couple.

In September, for example, Cuomo refused to endorse any candidate in New York’s mayor’s race, the New York Post reported, even though progressive de Blasio was a solid favorite to win re-election.

Then in November, the pair seemed to be fighting over who should be considered more “anti-Trump,” the Post reported, citing a fundraising letter in which the more centrist Cuomo urged his supporters to protest outside a Dec. 2 Trump fundraising event in Manhattan.

The Dems’ split traces to at least 2013, Vice reported, when Cuomo opted against fully backing de Blasio’s plan to fund pre-kindergarten classes for the city’s children. It was considered the then-new mayor’s signature policy proposal. (The Vice story carried the subtle headline, ""Why Bill de Blasio and Andrew Cuomo Hate Each Other's Guts.")

Joke from Clinton

The long-running tiff was even a source of public mockery from then-Democratic nominee Hillary Clinton at a New York political dinner just prior to the 2016 presidential election.

Her Republican rival, Donald Trump, was also in attendance.

“Your eminence,” Clinton said to the evening’s host, Roman Catholic Archbishop Timothy Cardinal Dolan, “you do deserve great credit for bringing together two people who've been at each other's throats — mortal enemies, bitter foes.

“I've got to ask: How did you get the governor and mayor here together tonight?”

"I've got to ask: How did you get the governor and mayor here together tonight?" — Hillary Clinton, joking about the Cuomo-de Blasio feud in October 2016.

De Blasio won re-election in November, becoming the first Democrat to return to City Hall in New York since Edward Koch won a third term in 1985.

Brooklyn bros

Why was Sanders the choice to swear in de Blasio? Perhaps because Sanders stumped for de Blasio during the mayoral campaign, where he referred to de Blasio as “the opposite” of President Donald Trump – a characterization undoubtedly popular with de Blasio’s progressive base.

“What this election here in New York is about is that everything that de Blasio is trying to do is exactly the opposite of what Trump is trying to do and you should all be very proud of that,” Sanders told a Manhattan crowd in October, Politico reported.

Aside from being ideological allies, Sanders and de Blasio also each have ties to Brooklyn. Sanders was born in the New York City borough, and de Blasio has called it home for many years.

The Associated Press contributed to this story.