Republican presidential hopeful Donald Trump's most enthusiastic supporters are predominantly white, lack college education, and bemoan their apparent marginalization in a rapidly changing America.
Their unexpected rise as a disruptive force in the 2016 Republican race has raised questions about who they are and what they espouse.
Confoundingly for Trump's rivals, so-called "Trumpeters" refuse to conform to conservative orthodoxy.
They come from throughout the vast United States, from rural, suburban and urban communities.
They extend well beyond niche voters, giving breadth and power to a campaign that was initially dismissed by GOP heavyweights and political pundits last year.
Trump has won an average of 37 percent of ballots cast in the 30-plus primary races to date; rich and poor, black and white, young and old have voted for him.
But experts working from exit polls say his core supporters are voters eager for a candidate who will tip the economic balance in their favor.
The demographic that routinely scores highest for Trump is those whose formal education ended with high school.
That is true in the US Northeast, where 47 percent of New Hampshire Republican primary voters with no college education picked Trump, and in the South, where that figure rose to 56 percent in Mississippi.
This hardly means college graduates shun the Donald. He often leads that group, too.
Those with advanced degrees spread their votes more equally among the candidates, however.
But with the Republican Party essentially a white bastion, the real estate mogul's most reliable base of support is caucasians with no more than a high school education -- about half of whom have voted for him so far in 2016.
- Eroding economic status -
Another variable that figures prominently in Trump's success: the proportion of voters who live in mobile homes. A New York Times analysis established a correlation between the number of mobile home in a county and the likelihood of it supporting Trump.
The more a region remained in the "old economy," with most jobs in agriculture, construction, trade or manufacturing, the more likely it would be to vote for Trump, the analysts found. The same could be said for the proportion of adults who are unemployed or have stopped looking for work.
The sense of slipping economic status featured prominently in exit polls conducted March 15 in five states including Ohio and Florida where about one in five voters said they felt they were "falling behind" with family finances.
Of those, about half voted for Trump.
"Trump is constantly telling voters how his own personal greatness will lead to prosperity," political science professors John Sides and Michael Tesler wrote in the Washington Post.
"It's a message that appears to resonate among Americans who do not feel prosperous."
- Race -
It is difficult to pinpoint the impact that Trump's anti-immigrant rhetoric has had on his political success. His call to ban Muslims from entering the country is popular not only among his followers, but with Republicans in general.
Few Republican candidates disapprove of Trump's proposal to round up and deport the 11 or 12 million undocumented immigrants living in the shadows.
But researchers have found that it is Trump in particular who has galvanized Americans worried about the country's ethnic diversity, notably its growing Hispanic population.
A pilot study in January by the American National Election Study found that the more voters give importance to their own "white identity" or believe that discrimination against whites is growing, the more likely they are to vote Trump.
- Unorthodoxy -
Trump's political positions often run counter to traditional conservative ideology, particularly regarding the role of government and his interest in curbing some excesses of free trade.
For example, he challenges free-trade principles by threatening tariffs on imports from China or Mexico. He also supports government helping ensure broader health care coverage or investing in modernizing the country's aging infrastructure.
Many voters who describe themselves as very conservative have expressed a preference for Trump's chief Republican rival, Ted Cruz, a Texas senator who adheres to conservative purity.
In the past, Trump defended abortion rights. University of Pennsylvania researchers whose work was featured on website FiveThirtyEight found Trump backers also had been more open to abortion in the past.
Researchers Dan Hopkins and Diana Mutz have followed a sample of US voters since 2007. They found that Trump supporters in the sample were far more supportive of abortion rights in 2007 than present-day Cruz backers were in the same year.