As recently as 1990, all but 7% of Americans claimed a religious affiliation, a figure that had held constant for decades. Today, 17% of Americans say they have no religion, and these new "nones" are very heavily concentrated among Americans who have come of age since 1990. Between 25% and 30% of twentysomethings today say they have no religious affiliation — roughly four times higher than in any previous generation. . . . Very few of these new "nones" actually call themselves atheists, and many have rather conventional beliefs about God and theology. . . .
Up until the 1970s, progressive Democrats were common in church pews and many conservative Republicans didn't attend church. But after 1980, both churchgoing progressives and secular conservatives became rarer and rarer. . . .
The fraction of twentysomethings who said that homosexual relations were "always" or "almost always" wrong plummeted from about 75% in 1990 to about 40% in 2008. . . .
From the early 1970s to the late 1980s the fraction of Americans age 18 to 29 who identified with evangelical Protestantism rose to 25% from 20%, but since 1990, that fraction has fallen back to about 17%. Meanwhile, the proportion of young Americans who have no religious affiliation at all rose from just over 10% as late as 1990 to its current proportion of about 27%.
From here (by Robert Putnam and David Campbell).
The authors express optimism that many young people will find religion as adults, although the historical data from secularization in Europe doesn't support that conclusion.
The resurgent generation gap, in which the young are more likely to use cell phones but not landline telephones and are politically different from older generations that are less likely to use cell phones only, is one reason that the Pew Research Center has cast doubt on the accuracy of landline only telephone surveys in this election, biasing the partisan make up of responses by as much as five percentage points (far more than in any prior election).
If the Pew Research Center is right, this year could be a Dewey v. Truman election, with Democrats outperforming polling expectations across the board and holding onto many more seats in Congress than predicted.