The Democratic primary field has been the most diverse in history, featuring African-Americans, women, a Latino, an Asian-American and a man in a same-sex marriage. The lineup has Democrats bragging about how their offers represent modern America, tempered by worries about the ''electability'' of the nontraditional candidates.

But according to a Gallup poll released Tuesday, Americans overwhelmingly are just fine with voting for a woman, as well as a black, Hispanic or (to a somewhat lesser extent) gay candidate. The sort of candidate a majority of Americans reject?

Socialist.

The category was the only one which had a majority of Americans, 53%, declaring they would not cast a ballot for a candidate so described (45% say they would vote for a well-qualified socialist).

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The numbers are a bit of a warning bell for Sen. Bernie Sanders , a self-described Democratic socialist who is a top contender for the Democratic nomination for president. President Donald Trump has repeatedly thrown out the word ''socialist'' to tar Sanders, Democrats as a party, and various policy initiatives such as Medicare for All.

And while several of the remaining Democratic primary candidates are repeatedly quizzed about their electability – Sens. Elizabeth Warren of Massachusetts and Amy Klobuchar of Minnesota often asked to defend a woman's ability to occupy the Oval Office for the first time — Gallup's poll shows it is Sanders who potentially has the biggest branding problem with voters.

The study found a strong willingness to vote for a presidential candidate who is African-American (96%), Catholic (95%), Hispanic (94%), and Jewish or female (93% each). Support was somewhat weaker for an evangelical Christian (80%) and a lesbian or gay candidate (78%). Age also matters somewhat: 70% said they would vote for a presidential contender under 40 (as former South Bend, Indiana mayor Pete Buttigieg is) and 69% said the same for someone over 70, as describes four major contenders — Sanders, Warren, former vice president Joe Biden and former New York City mayor Michael Bloomberg.

''As the 2020 Democratic presidential primaries get underway, it may be instructive to know that little prejudice stands in the way of Democratic as well as national support for candidates who happen to be Catholic, Hispanic, Jewish or female,'' the Gallup report on its poll said.

But the term ''socialist'' makes American voters squeamish, the poll found. More voters were willing to vote for a Muslim (66%) or an atheist (60%). And ''socialist'' was the only category of candidate for which the percentage of voters willing to cast a vote for such a contender actually went down from the previous survey, in June 2015.

Sanders has arguably the most devoted and loyal following in the Democratic field, and he and his surrogates argue that the enthusiasm he inspires among young people will put him over the top in the primaries and the general election.

But several of his challengers disagree. Biden warns that a candidate with ''socialist'' anywhere in his description will endanger the prospects for down-ticket candidates in swing districts, where independent and moderate voters might choose to stay home rather than vote.

Klobuchar was the only candidate to raise her hand when a moderator at Friday night's debate in Manchester asked contenders if they were concerned about a socialist nominee. ''I am troubled by having a socialist lead our ticket,'' the Minnesota senator said on CBS Monday.

Buttigieg, at a rally in Keene, N.H. over the weekend, criticized the ''revolution'' rhetoric of the Granite State front-runner as divisive. ''This is a moment for bringing as many people as we can into the picture, but a picture where your only choices are between a revolution or the status quo is a picture where most of us don't see ourselves,'' Buttigieg said, not mentioning Sanders by name.