There’s a big, big difference between being a true follower of Jesus of Nazareth and calling yourself a “Christian”. Putting that aside, the percentage of Americans who say they’re Christians has been going down, while those who claim to be have become more more fervid in their political beliefs.

[According to the Pew Research Center,] since the 1990s, large numbers of Americans have left Christianity to join the growing ranks of U.S. adults who describe their religious identity as atheist, agnostic or “nothing in particular.” This accelerating trend is reshaping the U.S. religious landscape….

The Center estimates that in 2020, about 64% of Americans, including children, were Christian. People who are religiously unaffiliated, sometimes called religious “nones,” accounted for 30% of the U.S. population. Adherents of all other religions – including Jews, Muslims, Hindus and Buddhists – totaled about 6%.

Depending on whether religious switching continues at recent rates, speeds up or stops entirely, the projections show Christians of all ages shrinking from 64% to between a little more than half (54%) and just above one-third (35%) of all Americans by 2070. Over that same period, “nones” would rise from the current 30% to somewhere between 34% and 52% of the U.S. population.

Brynn Tannehill, writing for The New Republic, considers what that may mean for our politics:

As American youths leave home, they leave the faiths of their parents and never return. This is in great part because the teachings of most churches in the U.S. are fundamentally at odds with what young people believe: particularly on topics like abortion, marriage equality, birth control, and premarital sex. They simply fail to see how such out-of-touch institutions are relevant….

The most crucial factor is how Christianity has slowly become primarily a political identity for many (overwhelmingly conservative) people. Over the past 40 years, membership in nice, bland, mainline Protestantism has plummeted, from 30 percent of the public down to 10 percent. Conversely, evangelical membership (and the number of white evangelicals) boomed in the 1970s and ’80s and then slowly declined. But evangelical groups are still much larger than the mainline Protestant denominations, constituting about 23 percent of adults and up to 37 percent of Americans claiming to be “born again.” Because white evangelicals are one of the most consistently conservative groups in the country, the result is that people who identify as Christian or attend church frequently are far more likely also to identify as Republican.

Black churches have held steady for decades at about 8 percent of the population. They are still associated with social justice goals, but they can also tend toward social conservatism, which can produce tension….Latinos were traditionally part of the Catholic Church. However, traditionally white evangelical denominations have had some luck luring Latinos away with social conservatism and the false machismo projected by Republicans, which explains some of the electoral shift seen in 2020.

Just as those who attend church frequently tend to be Republican, the converse is also true: Those with no religion are far more likely to be Democrats. Data analysis by Ryan Burge shows that white evangelicals have had a stranglehold on the [Republican Party] for over two decades and form a clear majority, alongside conservative Catholics. However, by 2018, the “nones” represented a plurality (28 percent) of Democrats, whose gains have come at the expense of evangelicals, mainlines, and Catholics within the party. Today, almost half of Gen Z has no religion….

A 2017 survey of 2,002 U.S. adults age 23 to 30 who attended a Protestant church … in high school found that 66 percent had stopped attending church. Seventy percent of those cited religious, ethical, or political beliefs for dropping out. Other major reasons cited included hypocrisy, churches being judgmental, and a lack of anything in common with other people at the church.