A presidential candidate who seeks to win the support of evangelicals -- who account for one-fifth of the electorate -- will find that their opinions are similar to those of nonevangelicals on a number of key voter issues.

The latest Gallup survey shows, for example, that evangelicals and nonevangelicals have similar attitudes toward gun registration, building more nuclear power plants, the death penalty for murder, and government social programs.

Furthermore, the differences on other key issues are perhaps not so great as might be expected. For example, 66 percent of nonevangelicals favor the Equal Rights Amendment, but so do 53 percent of evangelicals. When it comes to icreased defense spending, 68 percent of nonevangelicals and 78 percent of evangelicals are in favor of stepping up spending for the military.

On issues related to personal morality and religion, however, major differences are found.

For example, half the proportion of evangelicals as nonevangelicals favor allowing homosexuals to teach in the public schools.

On banning abortion, 29 percent of nonevangelicals express support for such action while 41 percent of evangelicals do so -- a pronounced difference, but perhaps less than one might expect.

The sharpest difference in views is found in reguard to prayer in schools. Even when this issue is posed in terms of requiring prayer, 81 percent of evangelicals vote in support while 54 percent of nonevangelicals do so.

Evangelicals, as defined in this survey, are likely to be women, living in the South, middle-aged, slightly downscale and more likely to live in rural areas.

In addition, evangelicals are slightly more Democratic in their political orientation than the rest of the nation and slightly more conservative.

Evangelicals are defined as those with three basic characteristics.

They describe themselves as with three basic characteristics: "born-again' evangelical Christians, or say they have had a "born-again" experience.

They have tried to encourage other people to believe in Jesus Christ.

They believe in a literal interpretation of the Bible, or the absolute authority of the Bible.

Nineteen percent of persons surveyed met all three of these criteria, which projects to about 30 million U.S. adults. While President Carter and Ronald Reagan are in close contention nationally, Carter is the overwhelming choice of evangelicals.

Being identified as a "born-again" evangelical Christian is on balance more a political asset than a liability. Although a 78 percent majority of nonevangelicals indicate that it would make no difference in their preference whether a presidential candidate was born-again Christian, the nation's evangelicals are highly partisan toward an evangelical candidate.

These findings are based on two in-person surveys, each with over 1,500 adults, 18 and older, conducted in more than 300 scientifically selected localities across the nation during Aug. 1 through 4 and 15 through 18.