But evangelical churches are also experiencing a decline in attendance…That bucks older conventional wisdom that conservative equals growth. In recent years, conservative denominations such as the Southern Baptist Convention, the Christian Reformed Church and the Lutheran Church-Missouri Synod have reported plateaus or losses.

Bleak and bleaker.

That’s the assessment of a new report on the state of American religious congregations.

Many “Oldline Protestant” churches are showing little spiritual vitality, and their small, aging congregations are showing little of the openness to the kinds of changes that might turn things around.

Many Evangelical Protestant churches, which once seemed to be bucking these trends, are stalling out as well.

Yes, of course, there are vital and growing congregations, says the report’s author, David Roozen of the Hartford Institute for Religion Research.

But the overall trend is clear, Roozen said of the 2010 survey of more than 10,000 congregations — Protestant, Catholic, Jewish, Muslim and Baha’i. It compares results with a similar survey a decade ago and smaller ones in between.

By several measures, the report said, religious congregations’ health is declining. That, Roozen said, fits with other research showing a rising number of people who claim no religion or to be spiritual but not religious.

“Despite bursts of innovation and pockets of vitality, the first decade of the twenty-first century witnessed a slow, overall erosion of the strength of America’s congregations,” begins the report, “A Decade of Change in American Congregations: 2000-2010.”

The report reflects a continuing survey project called Faith Community Today, which measured congregations in 27 denominations or other religious categories.

Attendance is down, money is down, conflict is high and, even by their own measure, congregations have less spiritual vitality than they used to.

The worst news, Roozen wrote, is for what traditionally is called Mainline Protestantism because of its onetime cultural prominence, including the nation’s largest Episcopal, Methodist, Presbyterian and Lutheran denominations.

Roozen calls them “Oldline Protestants,” and he said the stark demographic reality is that their overwhelmingly aging members cannot be expected to live much longer.

Their congregations can’t be feeling so good themselves, to paraphrase the late columnist Lewis Grizzard’s reaction to Elvis’ death.

“What’s interesting is how old the Oldine really is,” Roozen said in a statement. “Half of the congregations could lose one-third of their members in 15 years.”

Sixty-three percent of Oldline congregations report a weekly attendance of 100 or less, compared with 56 percent a decade ago.