An Associated Press-NORC poll found nearly mirror-opposite partisan reactions to the question of what kind of culture is important for American identity. Sixty-six percent of Democrats, compared with only 35 percent of Republicans, said the mixing of cultures and values from around the world was extremely or very important to American identity. Similarly, 64 percent of Republicans, compared with 32 percent of Democrats, saw a culture grounded in Christian religious beliefs as extremely or very important.

These divergent orientations can also be seen in a recent poll by P.R.R.I. that explored partisan perceptions of which groups are facing discrimination in the country. Like Americans overall, large majorities of Democrats believe minority groups such as African-Americans, immigrants, Muslims and gay and transgender people face a lot of discrimination in the country. Only about one in five Democrats say that majority groups such as Christians or whites face a lot of discrimination.

Republicans, on the other hand, are much less likely than Democrats to believe any minority group faces a lot of discrimination, and they believe Christians and whites face roughly as much discrimination as immigrants, Muslims and gay and transgender people. Moreover, only 27 percent of Republicans say blacks experience a lot of discrimination, while 43 percent say whites do and 48 percent say the same of Christians.

Taken as a whole, these partisan portraits highlight contrasting responses to the country’s changing demographics and culture, especially over the past decade as the country has ceased to be a majority white Christian nation — from 54 percent in 2008 to 43 percent today. Democrats — only 29 percent of whom are white and Christian — are embracing these changes as central to their vision of an evolving American identity that is strengthened and renewed by diversity. By contrast, Republicans — nearly three-quarters of whom identify as white and Christian — see these changes eroding a core white Christian American identity and perceive themselves to be under siege as the country changes around them.

Americans of both political parties sense the unraveling of a broadly shared consensus of American identity, although they cite different reasons for feeling that way. About seven in 10 Republicans and Democrats fear that the United States is losing its national identity, the A.P.-NORC survey found. The two political parties may not share much, but each is increasingly aware that the other has embraced a radically different vision of America’s identity and future.