President Trump has a surprising phone pal: He and New York City Mayor Zohran Mamdani have texted back and forth recently, two sources familiar with their conversations tell Axios.

Why it matters: The back-channeling between the democratic socialist mayor and Trump — who once derided Mamdani as a "communist" — indicates their private communications have been more extensive than previously thought.

• It also suggests that the good vibes they presented during Mamdani's post-election visit to the Oval Office in November have developed into an ongoing relationship.
• The texting started soon after Trump and Mamdani exchanged numbers during their November meeting, the sources told Axios.

Zoom out: Trump and Mamdani's stunning show of congeniality during that meeting followed months in which they'd repeatedly insulted each other. Trump had warned New Yorkers that electing Mamdani would ruin the city, while Mamdani had called Trump a fascist.

• But they seemed to get along swimmingly in front of the cameras, once they met in person.
• Trump, in particular, lavished praise on Mamdani. "Wow, you are even better-looking in person than you are on TV," the president said when Mamdani entered the Oval Office, according to New York magazine.
• Mamdani also sought to charm Trump during their meeting, winning him over by chatting about New York City neighborhoods and a pharmacy the president's father had patronized.

Zoom in: It's unclear what subjects Trump and Mamdani have texted about, or exactly how often they've been lighting up each other's phones.

• Mamdani has plenty of reasons to keep up a good working relationship with the president, including preventing him from withholding money from the city, as he has threatened, or sending in National Guard troops.
• Trump, meanwhile, seemed to enjoy sharing the newly elected mayor's star power and his focus on affordability, a weak spot for Trump in polls.

Mamdani told Spectrum News NY1 in December that after their meeting he had a separate discussion with Trump to discuss building affordable housing in New York.

• Mamdani also expressed his condolences over the attack on National Guardsman in D.C.

What they're saying: Spokespeople for Trump and Mamdani declined to comment.

The intrigue: It appears that Mamdani and Trump's relationship may have hit a rough patch in recent days, though.

• Mamdani said at a press conference this month that he had called Trump to express his displeasure with the U.S. strikes on Venezuela and its capture of Nicolás Maduro.
• Trump later told the New York Times that he was "surprised" by Mamdani's comment and "thought it was awfully quick for him to be criticizing." Using the past tense, Trump said that "I did" have a good relationship with Mamdani, but "he hit me sooner than I thought."
• One top administration official was surprised Mamdani made the call and thought he was out of line in doing so.
• Mamdani, however, has downplayed the call's significance, saying that "the president and I have always been honest and direct with each other about places of disagreement."