Evangelist leaders joined forces with conservative politicians here last week in exhorting millions of nonvoting Christians to "crawl out from under those padded pews" and take up political arms in the equivalent of a moral war to save America.

The two-day gathering in the brimstone shimmer of 105-degree Texas heat was billed sedately as The National Affairs Briefing. But it was really a fusion of Bible-thumping revivalist oratory with hardline New Right politics.

Its goal: to get godly conservatives elected to offices high and low across the land.

"Not voting is a sin against almighty God!" thundered Texas evangelist James Robison, one of the meeting's organizers, a fearsome, red-faced orator, his face muscles straining, a Bible clenched in his upraised hand.

The Southern Baptist roof-raiser led a procession of speakers in denouncing "perverts, radicals, leftists, communists, liberals and humanists" who they say have taken over the country because Christmas didn't want to dirty their hands in politics.

"You became a fortress instead of a force," he told the crowd, estimated at 15,000 at its peak. "You stop criticizing the welfare program. You're the cause of it! You didn't want to get down there in the ditch yourselves!"

The bedrock born-again audience roared hallelujas and amens. Thousands sat attentively through more than 20 hours of exhorting and denouncing spread over Thursday and Friday. Some brought picnic hampers and thermoses so they wouldn't have to miss a word.

Orchestrated and color-coordinated for television in the modern stone "tent" of this city's Reunion Arena, the revival was sponsored by the Washington-based Religious Roundtable, founded by Ed McAteer, who was for 25 years in sales for Colgate-Palmolive before turning full time to religious activity.

The audience included laymen and several thousand preachers from 41 states, though most seemed to come from Texas and the Bible-Belt Southwest. Almost all white, middle-class and dressed in Sunday-best style, they were old and young, men and women, ranchers, ad salesmen, miners and businessmen, with a peppering of famous Texas multimillionaires.

Industrialist T. Cullen Davis, who said he had a born-again experience after his recent acquittal on a murder-for-hire charge, came to praise Ronald Reagan and told reporters he had helped finance the $450,000 gathering. Magnate Nelson Bunker Hunt was there, he said, just to enjoy the speeches. The Dallas Times Herald noted Hunt was out getting a soft drink when the evangelists took up the offering.

The crowd heard speakers ranging from Phyllis Schlafly, antifeminist leader of the Stop ERA movement, to a general who predicted a nuclear holocaust within a decade if America does not "turn to God" and beef up military defenses against godless communism. The repentant son of atheist crusader Madelyn Murray O'Hair urged that prayer be returned to the schools. Champions of the antiabortion National Right to Life Committee promoted their cause.

And throughout, attentions swung widly from theology and scripture to instruction on how to organize without violating tax laws, the practicalities of registering a congregation to vote during the Sunday service and the importance of keeping a "moral score card" on the voting record of elected representatives.

The movement's trademark is the word "VOTE" with an oversized cross in place of the T. Its leaders plan to salt the nation's fundamentalist churches with that emblem on lapel buttons and bumper stickers.

Many of the born-again faithful -- rural, traditionally other-wordly -- mixed gingerly at best with the iniquitous world of nuts-and-bolts politics, as represented by pragmatic political mechanics and politicians, mostly Republican.

Many of them "do not even watch ordinary television," noted one political operative with a trace of awe. "They may watch [the religious broadcasts] but they do not watch Walter Cronkite."

The gathering grew out of the fledgling movement founded largely by radio and television preachers such as Jerry Falwell of Lynchburg, Va., after they found in a survey that some 70 percent of those who identify themselves as born-again Christians (a group estimated at between 35 million and 60 million people) did not vote in 1976.

The movement, however, has yet to demonstrate a significant ability to turn out the born-again vote.

But it has shown enough promise to draw presidential nominee Reagan as a speaker Friday night in an appeal for Christian support.

Reagan tried to avoid getting specific on such flammable topics as homosexual rights, abortion and the Equal Rights Amendment during his stopover here.

But he raised some eyebrows when, in response to a question at a news conference, he questioned the theory of evolution, another favored fundamentalist target, and recommended that if that scientific theory is to be taught in public schools, then the biblical story of creation should also be taught.

The movement presented enough of a threat to provoke counterdemonstrations by a couple of hundred moderate or leftist political activists in a Dallas park. The evangelists also have stirred up controversy among some church leaders and politicians over whether they are violating the doctrine of separation of church and state.

The rally organizers repeatedly insisted their movement is nonpartisan and will make no formal endorsements but would "encourage" candidates of Christian principle. Most of those happen to be Republican, they conceded.

Some of the New Right political specialists at the arena expressed doubt that all this rhetoric and whipped-up excitement would be translated into discernible, focused power at the polls anytime soon despite a lot of media attention to it as a new trend.

"I think anybody looking for a revolution this year is going to be disappointed," said New Right guru Paul Weyrich in an interview. "The mechanism [for getting out the vote] just has not been set up yet. Until they do that, they're just a vague, amorphous group -- and vague doesn't win in politics."

Among those who came to the arena were Jim Butler and his wife, Donna, with their three children. A former mortician and hospital worker, he is studying to be a minister at a Dallas Bible college.

"We were like that -- we used to always just say let everybody else worry about it. Politicians never keep their promises anyway, he said. "But there's enough sinners in the White House and we see now the need to get out the vote for a godly man."

Which godly man? "I don't know," he said, shaking his head.

Di Di Dowell of Fort Worth and her sister Tedonna Delk of Texarkana also said their eyes had been opened in recent months by the evangelists' political campaign. The sisters are now working actively against ERA. "My attitude used to be, just wait for Christ's return," said Delk. "But now, for my children, for the family, I'm getting involved. I'm going to share this with 25 women in my group back home. I don't want to be stupid anymore."