Sen. John Glenn has drawn even with former vice president Walter F. Mondale for the first time in a presidential preference poll of registered Democrats, according to a new survey by the Los Angeles Times. A Mondale adviser labeled the poll "fundamentally out of step with all other available public data."

The Times' nationwide survey showed Glenn with 28 percent and Mondale with 26, a dramatic swing from the newspaper's survey a month ago when Glenn trailed Mondale, 34 to 17.

Conducted between May 8 and 12, the poll surveyed 442 registered Democrats nationwide and had a 5 percent margin of error, meaning that either candidate's percentage could be 5 points higher or lower.

Mondale has led handily in all previously published surveys of voter preferences among 1984 Democratic presidential candidates. The last public survey since Glenn announced his candidacy April 21 was conducted by Penn & Schoen Associates and had Mondale leading Glenn, 36 to 24. Those pollsters said Mondale's rating had declined slightly while Glenn gained.

"The Mondale strategy is heavily based on the premise that Walter Mondale has the nomination already locked up," the Times quoted Joseph Grandmaison, political director of the Glenn campaign, as saying. " . . . These numbers weaken Mondale's argument and strengthen Glenn's argument. It has a significant impact on winning support and raising funds for our campaign."

Mondale's acting chairman, James A. Johnson, said the Times figures are "14 to 28 points different from all other polls on the Democratic side."

After Glenn and Mondale in a listing that included eight candidates and three noncommittal categories came Jesse Jackson with 5 percent, Sen. Gary Hart (Colo.) and former California governor Edmund G. (Jerry) Brown Jr. with 4, and former Florida governor Reubin Askew and Sens. Alan Cranston (Calif.) and Ernest F. Hollings (S.C.) with 2 points. Twenty-seven percent answered Unaware, Someone Else or Not Sure.

Meanwhile, two prominent Democrats warned the party's national strategy council here yesterday that Democratic presidential candidates will court political disaster by pandering to special-interest groups.

New York Gov. Mario M. Cuomo and House Democratic Caucus Chairman Gillis W. Long (La.) mentioned no one by name. Mondale has the strongest support among interest groups such as organized labor.

Cuomo warned that Democratic candidates are "tempted to offer, instead of an intelligent approach and program, a string of swollen promises, each one designed to seduce a different interest group or constituency into a conspiracy of selfishness."

He added, ". . . Unless there is a real difference in what we believe, a real capacity to improve the conditions of people's lives, putting a Democrat in the White House will be only an exercise in political vanity . . . . If it becomes a simple competition of personalities, I and many others will have little motivation to struggle and even less expectation of victory."

Long said: "I'm concerned . . . that some presidential candidates already have begun an ardent courtship of narrow interest groups . . . . By taking that route, the American people instinctively know that candidates beholden to special causes are likely to have little political flexibility and even less stomach for making the tough decisions . . . ."

Long's caucus staff director Alvin From said Long referred to those who had supported labor's domestic-content trade restrictions, who have actively embraced National Education Association proposals and who rushed to Chicago to endorse Harold Washington for mayor, in hopes of securing blacks' support.

The council, in its third annual quest for a Democratic alternative to President Reagan's policies, discussed economic and tax proposals aired in Congress in the last year but adjourned without declaring a national party position on them. That will be done in the party's 1984 platform, national party Chairman Charles T. Manatt said.