Survey finds percentage of of Americans identifying themselves as Christian has fallen over two decades.

America is a less Christian nation than it was 20 years ago, and Christianity is not losing out to other religions, but primarily to a rejection of religion altogether, a survey published Monday found. Seventy-five percent of Americans call themselves Christian, according to the American Religious Identification Survey from Trinity College in Hartford, Connecticut. In 1990, the figure was 86 percent. William Donohue, president of the Catholic League said he thinks a radical shift towards individualism over the last quarter-century has a lot to do it.

"The three most dreaded words are thou shalt not," he told Lou Dobbs. "Notice they are not atheists -- they are saying I don't want to be told what to do with my life."

At the same time there has been an increase in the number of people expressing no religious affiliation.

The survey also found that "born-again" or "evangelical" Christianity is on the rise, while the percentage who belong to "mainline" congregations such as the Episcopal or Lutheran churches has fallen.

One in three Americans consider themselves evangelical, and the number of people associated with mega-churches has skyrocketed from less than 200,000 in 1990 to more than 8 million in the latest survey.

The rise in evangelical Christianity is contributing to the rejection of religion altogether by some Americans, said Mark Silk of Trinity College.

"In the 1990s, it really sunk in on the American public generally that there was a long-lasting 'religious right' connected to a political party, and that turned a lot of people the other way," he said of the link between the Republican Party and groups such as the Moral Majority and Focus on the Family.

"In an earlier time, people who would have been content to say, 'Well, I'm some kind of a Protestant,' now say 'Hell no, I won't go,'" he told CNN.

Silk also said the revelation that some Catholic priests had sexually abused children -- and senior figures in the church hierarchy had helped to hide it -- drove some Catholics away from religion.

And, he said, it is now more socially acceptable than it once was to admit having no religion.

"You're not declaring yourself a total pariah. The culture has changed in a way that makes it easier to say, 'No, I don't have a religion. Even in the past year, Mitt Romney and Barack Obama feel obliged to talk about 'those of no faith,' " he pointed out. Obama mentioned people without faith in his inaugural address in January, making him the first president to do so.