WASHINGTON — Many moderate Republicans, including veteran U.S. senators, have concluded with a mixture of alarm and amazement that the religious right--already a potent grass-roots force--is poised to take control of the national party and precipitate a political confrontation unparalleled since the rise of Barry Goldwater 30 years ago.

And, they say, middle-of-the-road Republicans have only themselves to blame: While Christian conservatives have worked tirelessly to take over party organizations at all levels from coast to coast, GOP moderates have remained passively on the sidelines, unwilling to fight with members of their own party over abortion and other explosive social policy issues that dominate the conservatives' agenda.

Unless their own wing becomes more aggressive, these mainstream Republicans warn, the religious right will reach Christian Coalition founder Pat Robertson's stated goal of winning "a working majority of the Republican Party" by 1996. And that could alienate millions of independent voters.

"If we let this thing continue to percolate without attacking it head-on," declared Pennsylvania Sen. Arlen Specter, a leading moderate, "we will assure President Clinton's reelection."

In 1964, Arizona Sen. Goldwater won the GOP presidential nomination after a grass-roots campaign by the conservative wing of the party but was mauled in the general election by Democrat Lyndon B. Johnson.

Although Specter reported some progress in a quiet campaign to persuade Republican senators to oppose addressing the abortion issue in the party's 1996 platform, he has not convinced Republican Party Chairman Haley Barbour or other GOP leaders. They have told him that failing to include an uncompromising anti-abortion plank would alienate Christian conservatives. The 1992 GOP platform called for a "human life amendment" to the Constitution, outlawing abortion in all circumstances.

Sen. Nancy Landon Kassebaum of Kansas, another GOP moderate, shares Specter's assessment. The religious right "has taken over a lot in Kansas," she said, "including my own county organization."

"Part of the problem," Kassebaum said, "is that moderates aren't willing to work in the trenches, while the Christian conservatives have gone door to door and worked hard and won control fair and square. My hat's off to them for that."