The four women who gathered the other afternoon in an office here did not look like revolutionaries. But a revolution is what took place here, as elsewhere in Texas, on Election Day. It has spurred the belief that in this key Sun Belt state the long- advertised realignment of the political parties may have taken place.

Mary Denny, the Denton County Republican chairman, is one of thousands who have flooded into this once-rural county from elsewhere in Texas (as in her case) or other states, responding to the economic opportunities created by the growth around the Dallas-Ft. Worth Airport Metroplex. She has been a Republican activist since she was a high school volunteer for Barry Goldwater in 1964. But she readily conceded that the powerhouse GOP organization she heads has benefited from the ideas and energy of migrants from the north who have made this the third fastest-growing county in the nation.

"A lady from Iowa introduced the idea of 'dollar night,' referring to a door-to-door canvass for small contributions to the GOP. "She didn't realize that it wasn't long ago that people here would not even admit being Republicans. But if it hadn't been for her, we would not have realized how many there are out there now willing to give to the Republican Party."

As early as the 1950s, conservative Democrats swung Denton County behind President Eisenhower, and later helped make John Tower and William Clements the first Republican senator and governor.

But going into 1980, Democrats still held a monopoly on local offices. That was the year Lee Walker, a 52-year-old native, decided to run for county commissioner. The decision came from a personal tragedy -- the rape-murder of her daughter. When the man accused of the crime was on trial, Walker came every day to the courthouse, and when the trial became more than she could stand, she would go into another room and listen to the proceedings of the commissioners' court, as the county board is called.

"There was no reason I could see that a woman could not do that commissioner's)$ job," she said. "And I really had a need for something different in my life, so I decided to go for it." Walker ran on the slogan "She's the man for the job," and became the first woman and the first Republican elected to a courthouse office.

Emma Jo Yarborough, the county Democratic chairman, recalled that, "Some people said it was a sympathy vote" that put Walker in office. But that same year, Jim Horn won election to the Texas house of representatives on his third try, giving Denton County its first Republican voice in Austin.

In 1982, another of the women in the room, Sandy Jacobs, joined Walker on the commissioners' court. Jacobs had moved down from Illinois in 1970 and had become active in the Republican women's club. She enlisted about 100 of her new friends as volunteers and won a shoe-leather campaign, even though Clements was defeated for reelection and Democrats scored well across Texas in 1982.

This year, everything fell into place for the Republicans. A third woman, North Texas State College political science instructor Ruth Tansy, was elected commissioner, giving Republicans their first majority. The GOP picked up the U.S. House seat in the district that included Denton County, won a second state legislative seat and every other office on the local ballot except for one constable post for which no Republican filed.

"We were unprepared for anything like this," said Democrat Yarborough.

The explanations start with what Houston political pollster V. Lance Tarrance calls "juxtapositional politics" at the top of the ballot. The Senate race between conservative Rep. Phil Gramm (R-Tex.) and liberal state Sen. Lloyd Doggett (D) reinforced the clear ideological split between President Reagan and Walter Mondale. Reagan carried Denton County with more than 75 percent of the vote, up from 59 percent in 1980, and Gramm won by almost as much, providing long coattails.

But in Denton County, at least, it would be a mistake to consider this simply a coattail conservative win. This year, people deliberately voted Republican -- even when the Republicans were clearly not the traditional candidates.

When I asked Ruth Tansy what worked best for her this year, she said unhesitatingly, "The phrase that became my favorite was, 'We don't need another good old boy.' newcomer and a college professor -- a 12-year county resident opposing Billy Joe Wilson, who digs stock tanks for the farmers and whose family has lived in the county for five generations. She ran on the unusual proposition that she was better trained to help run a fast- growing county government with a $17.5 million budget.

"We were the progressive candidates," said Sandy Jacobs. "We were the ones who said we need a 20-year plan instead of day-to-day decisions."

"The voters," said Lee Walker, "just got tired of the Democrats' saying, 'We've always done it this way.'

If this were unique to Denton County, it would still be a good human interest yarn. But the tide of change swept across Texas last month, raising questions about the future of politics in this vital state that will be examined in another report.