For president-elect Donald Trump, “Happy Holidays” is apparently nothing more than politically correct nonsense. For many conservatives, the phrase is just another example of the "war on Christmas" perpetrated by liberals.

Trump's attitude may be a welcome change for the evangelicals who helped him win the GOP primary and capture the White House. Trump won 81 percent of evangelicals, according to exit polls — more than Romney in 2012 or even Bush in 2004.

"You go into a department store," Trump said at Liberty University in January. “When was the last time you saw ‘Merry Christmas’? You don’t see it anymore. They want to be politically correct.”

An analysis of four years of Twitter data — more than 400 million tweets — by NBC News with linguistic and geography researchers from the University of South Carolina and Aston University found usage of "Merry Christmas" still common, especially in areas that were key to Trump's primary and general election wins.

The below map shows rural areas in the South and Rust Belt still say “Merry Christmas” much more than “Happy Holidays” on Twitter. In many cities won by Democrats, “Happy Holidays” is said more frequently, though it is still generally said less than “Merry Christmas.”

On average, 86 percent of holiday greeting tweets said “Merry Christmas.”

So why does Trump continue to claim "Merry Christmas" is waning in popularity? While Twitter is not a perfect sample — only about 21 percent of adults use it and it skews younger and more urban, according to The Pew Research Center — it is considered one of the best ways to understand language use in real-time.

One simple reason Trump champions "Merry Christmas" is because it appeals to key parts of his base.

The greeting is very popular among Bible Belt evangelicals, who, as shown in the below maps, tend to live in the states that formed Trump's core support in the primaries.

The term's use is also contested in these areas. Many evangelicals in the South live in areas with high religiosity but where there are racial and cultural divisions over which term to use. African-Americans in these areas prefer "Happy Holidays" and evangelical whites prefer "Merry Christmas," according to past polling, so while "Merry Christmas" is very popular in these communities among the majority populations, underlying that are diverse demographics with conflicting opinions.

Trump struggled with and needed to make inroads with evangelicals, who may have appreciated his support for the greeting. Eventually, he did, faring well with the group in the election.

"Merry Christmas" is also popular in areas where white voters came through decisively for Trump in the general election — Western Pennsylvania, most of Ohio and Appalachia, as well as rural North Carolina.

Although people in these places attend religious services less frequently, they say “Merry Christmas” a lot more and are in areas more likely to support businesses saying "Merry Christmas" instead of adopting "Happy Holidays." Voters in these areas are credited with having put Trump over the top in the general election.

Although the map below depicting areas of higher religiosity correlates well with "Merry Christmas" usage on Twitter, it should be interpreted with caution. The country's more religious states as a whole support saying "Merry Christmas" — but many are also religiously diverse or home to diverse urban centers that say "Happy Holidays" more often.

And these areas may have communities experiencing ethnic or cultural tension, one of the major themes of the 2016 campaign covered by NBC News. That conflict is at the heart of why the term takes on extra meaning among some groups, like evangelicals.

Polling and the geographic Twitter analysis also support the notion there is more upside than downside for Trump in taking a hard stance on the phrase.

A Public Policy Polling poll taken in early December found that Republicans strongly support saying "Merry Christmas" by a 65 percent margin. Sixty-three percent of Democrats, on the other hand, say it "doesn't make a difference" either way which term is used, and nationally only 4 percent of respondents say they are offended by the phrase. Independents were more likely to agree with Republicans that stores or businesses should not change their greeting to "Happy Holidays" from "Merry Christmas."

Geographically, "Happy Holidays" is found more often in urban areas with higher minority populations won handily by Clinton. As the map below shows, Clinton tended to win the coasts and the cities, areas where "Merry Christmas" usage is less popular.

Methodology

Twitter data is provided by Diansheng Guo and Yuan Huang (University of South Carolina), Jack Grieve (Aston University) of Spatialdatamining.org. An original corpus of November and December tweets taken from 2012 to 2015 was used to identify roughly 900,000 unique user Tweets containing variants on "Merry Christmas" or "Happy Holidays." Low-levels of spatial smoothing were applied to account for areas with lower numbers of tweets. Tweets from Spatialdatamining.org project has been used for past projects, like "The Great American Word Mapper," which have opened-sourced large datasets for those looking to do further analysis.