One of Donald Trump's campaign promises was to end the "war on Christmas."

Trump has doubled down on the importance of saying Merry Christmas — but Ivanka Trump has broken from her father by wishing people "happy holidays."

The split reveals a deeper divide between the two.

As Donald Trump campaigned for president, one of his promises to was to end the "War on Christmas."

"You go to stores, you don’t see the word Christmas," Trump said last year, the Washington Post reported. "It says 'happy holidays' all over. I say, 'Where’s Christmas?' I tell my wife, 'Don’t go to those stores.' ... I want to see Christmas."

Since becoming president, Trump has doubled down on his pro-Christmas message, recently filling a rally in Pensacola, Florida with "Merry Christmas" signs. On Tuesday morning, Trump changed his Twitter background to an image of people at the rally holding up letters to spell "CHRISTMAS."

Donald Trump Twitter

However, hours before, Ivanka Trump raised eyebrows when she shared her own festive greetings in Twitter, tweeting "Happy Holidays" on Monday evening.

Ivanka Trump Twitter

It makes sense that the first daughter, who is Jewish, would wish people happy holidays the day before Hanukkah begins.

However, that didn't stop many people on social media for poking fun at the tweet, in light of the president's comments on a war on Christmas.

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Ivanka's fashion brand similarly favors the more inclusive "holiday" language over "Christmas." So, even if Trump understands why his daughter personally would say "happy holidays," her business (which she is no longer involved in the day-to-day operations of) is doing exactly what he has campaigned against.

While most of the tweets were tongue-in-cheek, Ivanka Trump's use of "happy holidays" over "Merry Christmas" highlights tension between the first daughter and the president.

The duo recently publicly split in the Roy Moore campaign.

After Moore was accused of dating and sexually pursuing underage girls, Ivanka Trump told the Associated Press that she had no reason to doubt the victims and that "there's a special place in hell for people who prey on children." Trump, on the other hand, endorse Moore and was reportedly annoyed that Ivanka spoke out against the candidate, the New York Times reported.

More generally, many on the right have turned on Ivanka, as she and her husband, Jared Kushner, have been seen as moderating voices in the Trump administration. That applies to her fashion line as well — Republicans' perception of the Ivanka Trump brand has substantially fallen since May.