The Wisconsin primary carried some serious warning signs for Jimmy Carter, despite the trouncing he gave Sen. Edward M. Kennedy.

The signals came not from his Democratic rivals but from Republicans Ronald Reagan and John B. Anderson.

Both showed impressive strength in this liberal crossover state among groups that Democratic presidential candidates traditionally depend on -- groups Carter will need to win the general election, if he wins renomination.

Reagan, the overwhelming GOP front-runner, demonstrated strong appeal among conservative Democrats and independents, especially among blue-collar workers. Catholics and union members -- all important parts of the Democratic coalition.

Kennedy, with his pro-labor voting record and Catholic heritage, had hoped to score heavily among these groups. He didn't.

The state's 4th Congressional District, located on Milwaukee's south side, is a good case in point. In this white-ethnic, Catholic area, which has voted Democratic longer than any area of the state, Kennedy drew fewer votes than Carter, Reagan, George Bush or Anderson.

Anderson, self-proclaimed leader of a "new politics" movement, drew support on the opposite end of the political spectrum from Reagan -- liberals and well-educated young people, who normally voted Democratic.

He drew almost as many votes in the 2nd Congressional District, dominated by the Madison campus of the University of Wisconsin, as Carter and Kennedy combined.

Although Anderson's prospects for gaining the GOP nomination dimmed considerably with his third-place showing in the Republican primary, he continued to hold out the possibility of running as a third-party independent next fall -- a prospect Democratic national chairman John White envisions as throwing his presidency to Reagan.

Even more threatening to Carter's prospects in the fall were the large numbers of Democrats and independents who chose to vote Republican Tuesday. Given the choice of casting ballot in either primary, three of five persons picked GOP ballots, a higher percentage than any time since the 1950s when Wisconsin was a solid Republican state. More than twice as many independents, who often hold the balance in presidential election, voted Republican as Democratic.

No primary is like a general election. But Wisconsin's primary, where voters are given ballots for both parties and choose which to mark, resembled a general election more than any primary to date this year.

Reagan had 361,643 votes, Carter 349,299.

In the Democratic primary, Kennedy had 187,490 votes and California Gov. Edmund Brown Jr., who dropped out of the race last night, 77,372 in complete unofficial returns. On the Republican side, George Bush had 274,985 and Anderson 247,109.

Wisconsin has a long tradition of progressive politics. It was the first state to adopt strong workmen's compenstation, anti-lobbying and civil service laws, and it gave Eugene McCarthy and George McGovern important Democratic primary victories.

But Attorney General Bronson La Follette, grandson of the state's best known political figure, says, "I don't know if we deserve the reputation of being a liberal state anymore."

"We have what is supposed to be a progressive governor and a liberal state legislature, but the biggest thing going on in the statehouse is to see who can cut the most out of the state budget."

In part, this represents a dramatic shift in the national political dialogue. What pass as social issues are no longer poverty or social welfare. The social issues of 1980 are abortion and gun control.

Reagan's longstanding positions on these issues give him appeal to some voters he couldn't reach a few years ago.

According to an exit poll by ABC News yesterday, the conservative former California governor not only picked up half the votes of people who consider themselves conservatives, but also got as high a percentage of the middle-of-the-road vote as any rival.