Fewer than half of those who identify as evangelicals (45 per cent) strongly agree with core evangelical beliefs, according to a new survey by LifeWay Research and reported by the Baptist Press.
The research portrays two distinct groups: evangelicals by belief and self-described evangelicals.
'There's a gap between who evangelicals say they are and what they believe,' said Scott McConnell, the executive director of LifeWay Research, based in Nashville.
Meanwhile, 69 per cent of evangelicals do not identify themselves as 'evangelical'.
To establish whether people were evangelicals, LifeWay used a set of four questions about the Bible, Jesus, salvation and evangelism developed in partnership with the National Association of Evangelicals, and those who strongly agree with all four are considered to be evangelicals by belief.
According to LifeWay Research, 15 per cent of Americans are evangelicals by belief.
This contrasts with 24 per cent of Americans who self-identify as evangelicals.
The researchers found some significant differences between the two groups, including the fact that evangelicals by belief are more diverse than self-identified evangelicals.
While fifty-eight percent of evangelicals by belief are white, 23 per cent are African American and 14 per cent are Hispanic, and five percent claim another ethnicity. In contrast 70 per cent of self-identified evangelicals are white, 14 per cent are African Americans, 12 per cent are Hispanic, and 4 per cent claim another ethnicity.
Evangelicals by belief go to church more often than self-identified evangelicals. Seventy-three per cent say they attend services once a week or more, while 61 per cent of self-identified evangelicals do.
Meanwhile, the two groups are surprisingly similar politically: two-thirds of evangelicals by belief (65 per cent) are Republicans or lean towards the Republicans while 30 per cent are Democrats or lean towards the Democratic party, and 4 per cent are undecided or independent.
Sixty-four per cent of self-identified evangelicals are Republicans or lean Republican, while 33 per cent are Democrats or lean Democratic, and 3 per cent are undecided or independent.
'The political differences between them turn out to be very small,' McConnell said.
African Americans, meanwhile, are more likely to say they are 'born again' (49 per cent) than whites (27 per cent), Hispanics (24 per cent) or those from other ethnicities (19 per cent).
And African Americans are also the most likely to have evangelical beliefs (30 per cent).
McConnell said that some research groups in the past limited the term 'evangelical' to mean white Christians.
'For many African Americans, the term "evangelical" is a turn-off, even though they hold evangelical beliefs,' he said. 'The term "evangelical" is often viewed as applying to white Christians only. And that's unfortunate. It's lost some of its religious meaning that actually unites these groups.'
