Just 46% of American adults are white Christians, down from 55% in 2007, according to the survey, published Monday by National Journal's Next America project.
And while the percentage of white Christians fell, they still make up 69% of Republicans. On the other hand, white Christians account for 31% of Democrats.
Among non-white Christians, 32% identify with or lean toward Democrats, and just 13% do the same with Republicans.
Experts say the shift is partially due to the country's increasing ethnic diversity and the growing number of Americans who don’t have any religious affiliations.
According to the survey, in 2007, 88% of white Republicans and 70% of white Democrats identified as Christian. By 2014, 84% of white Republicans identified as Christian, but the share of white Democrats identifying as Christian fell to 57%.
Pew conducted the survey by telephone between June 4 and September 30, 2014, interviewing 35,071 Americans, with an overall margin of error of plus or minus 0.6 percentage points.