(RNS) The road to the White House is no longer white and Christian.

President Obama won last week with a voter coalition that was far more racially and religiously diverse than Mitt Romney’s – a phenomenon both predicted in the days before the election and confirmed in the days after.

What the Public Religion Research Institute has concluded since, however, has farther-reaching implications: that relying on white Christian voters will never again spell national electoral success -- especially for the GOP.

“The changing religious landscape is presenting a real challenge to the strategy that relied on motivated white Christians, particularly white evangelical Christians,” said PRRI Research Director Dan Cox, referring to a PRRI study released Thursday (Nov. 15).

“They’re still turning out at similar levels as they did in previous elections, but their size in comparison to other groups is shrinking.”

Obama’s religious coalition was a diverse mix, including 13 percent white mainline Protestants, 8 percent white evangelical Protestants, 10 percent Hispanic or other Catholics and 13 percent white Catholics, and 16 percent black Protestants. His largest subgroup of “religious” voters was the unaffiliated – those that do not identify with a religious group -- at 25 percent.

Compare that to Romney, whose largest subgroup of religious voters – white evangelical Protestants – accounted for a full 40 percent of all his votes. Add in other white Christians and Romney’s total white Christian vote count was 79 percent. By contast, white Christians represented 35 percent of those who chose Obama.

So many white Christian eggs in one electoral basket would not be a problem for candidates if the supply of these voters growing. But it’s not, according to studies, even as the white Christian proportion of Republican presidential voters – about eight in 10 -- has held fairly steady for the last six elections, according to national polls.

At the same time, the proportion of white Christians voting for Democratic presidential candidate has declined, from about six in 10 in 1992 to less than four in 10 last week.

These trends dovetail with the striking growth of religiously unaffiliated voters, who represented about 7 percent of all Americans in the early 1990’s and nearly one in five today. Unaffiliated voters tend to be young, and though they don’t get themselves to the polls as reliably as other voters, their influence on American elections and culture will only continue to increase, said Cox.

The term used by demographers is “generational replacement,” and in this case, younger unaffiliated voters are replacing the older Christian ones who preferred Romney to Obama.

“You see tectonic shifts when one generation looks very different from the generation it’s replacing,” Cox said.

The study of 1,203 voters, which has a margin of error of plus or minus 3.5 percentage points, was conducted from Nov. 7-12.

KRE/DBG END MARKOE