The hard core of the conservative movement gathered here yesterday to hear President Reagan warn of the dangers of complacency, and to stage the first major right-wing presidential cattle show to test the ideological credentials of those who might seek the 1988 GOP nomination.

The president told 2,000 enthusiastic conservatives that "we must tell the American people that the progress we made thus far is not enough, that it will never be enough until the conservative agenda is enacted and that means enterprise zones, prayer in the public schools and protection of the unborn."

Referring to declining contributions to major conservative groups, Reagan warned that the movement is in "danger of growing soft with victory, of losing perspective when things go our way too often."

The president also said, "tell your volunteers and your contributors that the president said they are needed now as never before . . . . The Washington liberals and the San Francisco Democrats aren't extinct. They're just in hiding."

Reagan's call for continued vigilance in the sixth year of his conservative presidency reflects the problems facing an ideological movement that played a significant role in changing the fabric and content of American politics.

"The conference you are attending today is in many ways unique," David Keene, the chairman, said at the start of the Conservative Political Action Conference. "This is the first time in 20 years that the heart and soul of the conservative movement hasn't been owned by a political figure."

With Reagan constitutionally barred from seeking a third term, Keene said, "There is no one today who can claim to be the conservative candidate."

If the conservative movement is up for grabs, all but one of the well-known prospective candidates for the Republican nomination plan to bid for a piece of it at the conference:

The starting gate will open at 8 this morning with speech by the Rev. Marion G. (Pat) Robertson, head of the Christian Broadcasting Network. He will be followed by Rep. Jack Kemp (R-N.Y.), former U.N. ambassador Jeane J. Kirkpatrick; former Delaware governor Pierre S. du Pont IV, and Senate Majority Leader Robert J. Dole (R-Kan.).

The presidential jockeying will conclude with a dinner address by Vice President Bush, at whose side will be Jonas Savimbi, leader of Angolan anticommunist rebel forces, and the Rev. Jerry Falwell, head of the Liberty Federation, formerly the Moral Majority. The only no-show is former Senate majority leader Howard H. Baker Jr. (R-Tenn.).

The conference is run by four of the organizations that helped found the modern conservative movement in the early 1960s -- the American Conservative Union, Young Americans for Freedom, the weekly paper Human Events and the magazine National Review. "Twenty years ago, these groups were the conservative movement," Keene said.

In addition, about 55 other organizations have contributed $1,500 each to sell memberships, issue papers and distribute election paraphernalia in exibition booths.

As part of the cattle-show atmosphere, conservative pollster Arthur J. Finkelstein is to survey members of the participating organizations to determine the presidential favorite.

Last year, Kemp won a similar staw poll at the CPAC convention, and Bush came in a respectable second. Bush aides hope the 1986 results will show that their boss has support on the political right.