Atheism and socialism are the two most unpopular characteristics for a US presidential candidate, according to Gallup research.

Figures show that Americans would rather elect a Muslim to be President than an atheist or a socialist.

If their party put forward an atheist candidate, only 58 per cent of Americans said they would vote them. This figure fell to 47 per cent if that candidate was a socialist.

However 60 per cent said they would vote for a Muslim candidate and 74 per cent for a gay or lesbian candidate.

Interestingly the proportion of those who would support a Catholic candidate (93 per cent) is significantly higher than those who would support an evangelical Christian candidate (73 per cent).

These figures reveal the uphill struggle faced by Bernie Sanders, the independent senator standing for the Democratic nomination, who is widely perceived to be both an atheist and a socialist.

Although the Vermont senator has said he is "proud to be Jewish", he added "I am not particularly religious."

On another occasion he described his belief in spiritualist terms: "Every great religion in the world — Christianity, Judaism, Islam, Buddhism — essentially comes down to 'do unto others as you would like them to do unto you,'" Sanders said.

"I believe that what human nature is about is that everybody in this room impacts everybody else in all kinds of ways that we can't even understand. It's beyond intellect. It's a spiritual, emotional thing."

Despite these soundbites, Sanders is widely perceived as an atheist.

These obstacles prove even more significant when the Pew research centre's statistics are taken into account. These reveal despite a rise in atheism, agnosticism and religious unaffiliated people in the US, non-religious people are shockingly underrepresented in Congress.

Not a single member of the current Congress is an admitted atheist and only one has declared themselves "religious unaffiliated".

This is despite the fact seven per cent of Americans are either atheist or agnostic and almost 16 per cent religious unaffiliated. However this trend has not transferred to the corridors of power.

"[A]ccording to our recent survey, being an atheist continues to be one of the biggest potential liabilities for a hypothetical presidential candidate, with roughly half of Americans saying they would be less likely to support a candidate who does not believe in God," Pew senior researcher Jessica Martinez told ATTN:.

"I would also point out that while about half of Americans say they would be less likely to support a presidential candidate who does not believe in God, the share who say this has been declining over time."