President Reagan's chief political adviser told key midwestern Republican women meeting here this weekend that the "gender gap" is threatening the president's reelection chances, if he chooses to run again, and could "lock" the Republicans "into the status of a minority party" for another generation.

Voter turnout projections "suggest that the political party that gets the women's vote will be the majority party, while the party of the men will be the minority," Reagan assistant for political affairs Edward J. Rollins said. This could make the early 1980s "a turning point in American political history . . . . In 1984, more women than men will vote," he said.

Rollins said that in a sample of 1982 midterm elections that he studied, Democrats ranged from 5 to 15 percentage points better among women voters than among men voters, he said, and studies of TV exit polls show that in 73 of 85 randomly selected races, Democrats did better than Republicans among women voters.

Polling data show that the Democrats have a 31 percentage-point edge in support from single women, Rollins said. He attributed this in part to the support that Democrats receive from working women, who outnumber their nonworking counterparts by 3 to 1, and said that this "enormous wave of demographic change sweeping the country" threatens "to swamp Republicans."

Rollins later said that the administration's goal is to win the same 48 percent of the women's vote that it got in 1980, but the most recent polls show that only 30 percent of women say they would vote for Reagan.

"The 'gender gap' is the clear result of the changing status of women," Rollins said. "Out from the shadows of their husbands, women have behaved differently than men in the voting booth in accordance with their inherent nature and also in accordance with their new experience as workers."

As laughter broke out in the audience at the Republican Women's Leadership Conference, Rollins turned red and added: "Boy, that's a chauvinistic statement if I ever heard one. I must have written that early this morning."

Rollins elicited more laughs later when he called Elizabeth Hanford Dole "the first transportation secretary of her sex."

According to Republican polling data, the heart of the "gender gap" is among women between 25 and 40. Richard Wirthlin, the president's pollster, said in an interview last week that the issues that concern women have changed since Reagan's election, with the economy--not nuclear arms--foremost now. Abortion and the Equal Rights Amendment are not issues, according to Wirthlin.

However, Kathleen A. Frankovic, director of surveys for CBS News, said last week that even with an upturn in the economy, she does not think Reagan can close the "gender gap" that is based on economic issues.

"I would argue that there are differences between men and women in their perception of how he is handling the economy," she said. "Men more than women say the recovery is at hand."

The latest Washington Post-ABC News poll shows that 55 percent of the male respondents approve of Reagan's handling of the economy, while 41 percent disapprove. For women, it is the reverse: 54 percent disapprove, while 42 percent approve.

Such polling data alarms White House advisers who say they think that this gap with women voters--as well as the alienation of blacks and Hispanics--could doom Reagan and the GOP in 1984.

Adding to the problem for the White House is the refusal of key women in the administration--particularly Faith Ryan Whittlesey, head of the public liaison office--to acknowledge a potentially long-term "gender gap." According to sources, Whittlesey thinks the gap is a result of the recession and will disappear with the recovery.

One White House answer to Reagan's problem with women voters has turned out to be a problem itself: an equity package of revisions in insurance, pensions and fair-wage laws to benefit women has stalled under opposition from the insurance industry and fears that it could hurt women by increasing their insurance premiums and pension deductions.

The weekend conference, attended by about 100 women and a Who's Who of the administration's women appointees, focused on giving those in attendance information to defend the president--particularly on his economic and arms policies--before other women. There was also a push to get the women to agree to put their names on the ballot in 1984 next to Reagan's.

"That's the best endorsement there is," said Betty Heitman, co-chairman of the Republican Party, who organized the conference. "Right now we don't have enough women standing up for the president. We have a good story to tell if these women will tell it."

"It's a tough one for us," Rollins said about the nuclear arms issue. "It's an issue that without question cuts against the administration, especially among women."

Two items not on the agenda were the Equal Rights Amendment and abortion, both of which Reagan opposes. Diane Stadtmueller, co-chairman of the Iowa Republican Party, said the women are turning away from these issues for now and seeking a "common ground" from which to build support for the president.

However, Pat Bergman of Aurora, Ill., who has managed several state campaigns, reflected widespread sentiment here with a necklace that spelled "E-R-A." Bergman said she supports Reagan but believes that ERA and abortion are issues that taint him as being opposed to women's rights.

"You have to realize he's 72 years old," Bergman said. "He's from another generation. Today we're talking to women voters in campaigns and their eyes will glaze over when you say you're a Republican. Say you're for ERA and they'll ask the name of your candidate."