A decade ago at the first convention of the National Women's Political Caucus, participants couldn't have themselves paged in the lobby of Houston's Rice Hotel. The reason? No "self-respecting" woman, the management said, would want to hear her name broadcast like that.

The Rice Hotel is no longer in business, and at this year's caucus, the 2,000 women have other things on their minds. Like electing the next president.

The caucus opened this morning in an open-air theater on the banks of the San Antonio River, and by late Saturday, every Democratic presidential candidate except Reubin Askew will be here looking for votes. The trick is to turn the "gender gap"--which shows that women, the majority of the electorate, vote significantly differently than men--to their favor. As Texas Gov. Mark White put it to cheers this morning: "You have the potential to determine who will be the next president of the United States!"

They're already attacking the present one. Kathy Wilson, the Republican who chairs the bipartisan caucus, has said that Ronald Reagan "seems to think his mandate is to rebuff our gains over the past 10 years," then complained of the "superficial, bandaid approach of the White House." Or, as White said to laughter at the opening ceremonies: "The man in the White House hasn't completely understood the gender gap. He thinks that's sitting closer to Mrs. Reagan at breakfast."

Initially, there had been talk of a straw poll on the presidential candidates, but the Democratic delegates were pressured by the candidates not to do it, and the Republican delegates decided that voting against Reagan wouldn't do them any good in the party.

"Can you see any reason to do it?" said Mary Stanley, the national chair of caucus Republicans. "Some of our people who are developing some clout within the party organization would lose it."

There is also talk of a possible presidential endorsement--a first for the caucus--but so far, it's just talk. The caucus, formed in 1971 as the political arm of the women's movement, is primarily dedicated to electing women to political office.

Today was spent in workshops that ranged from how to run your political campaign to feminist strategies in the arms race to what lesbians should do about AIDS. Working the crowds that drifted through San Antonio's convention center were staffers of John Glenn, Walter Mondale, Gary Hart et al., asking the women to come to their breakfast and drop by their reception. It was a new courtship, and the women loved it.

"We lobbied, we educated, we pleaded, we negotiated, we even prayed for equality--but it was not ours to have!" said Bella Abzug, shouting and shaking her fist in an emotional speech that left her breathless. "The gender gap is merely a suppressed expression of women who felt powerless outside the power structure!"

Along with the rhetoric came some pragmatic advice. In a workshop called "Targeting for Victory--Where to Put Your Resources," Ann Lewis, the political director of the Democratic National Committee, outlined some basics: When you run for office, get your hands on every list of working women you can think of, including registered beauticians. One of every 44 registered women voters is a nurse--so get that list, too.

And don't forget the community activists, either. "When you start looking at who organized to close down that toxic waste dump, or who organized to put up that stoplight," she said, "ninety percent of those people are women." Almost everyone in the room took notes.

Later in the day, at one of several "dialogue lunches," feminists working against the arms race warned that women have to know the facts--or end up "marginal to the movement, making coffee and Xeroxing--like we did in the peace movement of the sixties."

And at a meeting of lesbian caucus members, the concern was AIDS, the disease that's frightening the homosexual community. "We can't get AIDS," one of them said, "but our brothers are dying." Jean Craciun, who works for a sexual assault agency in Anchorage, Alaska, had a different view. "When I was coming out years ago to my mother," she said at the meeting, "the way I could help her to accept it was to get her to stop focusing on the sex. With this AIDS thing, it's happening again. It's getting to be focused on sex."

The real business of the convention begins Saturday, when Wilson delivers a speech that is said to be a strong attack on Reagan. On Sunday, the presidential candidates will answer questions in a forum moderated by Harriett Woods, who lost the 1982 U.S. Senate race in Missouri and now plans to run for lieutenant governor in 1984. Everybody wants to get a crack at them.

"They're all saying the right things about women," said Frances (Sissy) Farenthold, the first national chair of the caucus, "but I don't know if they'd take a woman running mate, or if they'd take a woman White House counsel. We have a gender gap, and it was marvelously successful for some male candidates--but we haven't seen it work for women yet."