In the West Texas town of Ozona, a quiet revolution of sorts was accomplished at the polling booth on a hot Saturday in August.

After four years of gerrymandering and stuffing of ballot boxes by Anglos, Crockett County elected its second Mexican American to the county commission, Hispanics, after decades of being ignored, had finally achieved full political equality on the four-member board.

Things went differently in Aransas County in South Texas. After the Anglo candidate for justice of the peace died, his supporters ran newspaper ads urging voters to elect him anyway over his Mexican-American opponent.

They did.

It has been that kind of year for Mexican-American political fortunes in the Southwest - some gains, some losses. They gained, for example, a state legislative seat in San Antonio, and they lost their city councilman in San Diego in 100 years when the council removed him after a misdemeanor conviction.

"On balance, it's been a year of losses," said Willie Valesquez of the Southwest Voter Registration and Education project, citing the loss of such high visibility officeholders as New Mexico Gov. Jerry Apodaca and the doomed Senate candidacy of that state's attorney general, Toney Anaya.

But if this election year has failed to increase significantly the numbers of Mexican-American officeholders, the Hispanic voter in the Southwest is nevertheless finding new power in influencing contests between Anglos.

Many officials are up for reelection or election now for the first time since the Voting Rights Acts was extended to language minorities, and Mexican Americans are finding themselves courted and fought over by Anglos of both parties in statewide races.

Organizers even talk boldly of the "Hispanic vote" in two large states, California and Texas, possibly determining the outcome of the 1980 presidential election. Already this year they have provided a primary election victory for John Hill, the Texas Democratic gubernatorial candidate, and will probably be the swing vote in Texas Senate race.

This political voice from the urban barrios and the rural villages, from the lush fields of the Rio Grande Valley and the dry dusty towns of West Texas and from the teeming Hispanic metropolis that lies within Los Angeles bears listening to nationwide.

For within a decade, Mexican Americans and other Hispanics - the Cubans in Miami, the Puerto Ricans in New York, the varied Latino groups in Chicago and elsewhere - will be the nation's largest minority.

Today, they are newly organized and beginning to overcome the political oppression and apathy that has characterized their voting. They are building toward political power in the next decade, making gains in obscure offices this year that they hope can be transformed into formidable candidates for higher offices in years to come.

In cities as distant and dissimilar as El Paso and Chicago, where a Hispanic voter registration drive is about to begin in earnest, Paul Moreno and Carlos Ponce strike this same theme.

"The real political fortunes of Hispanics will be determined by how many are counted in the 1980 census," says Ponce of Chicago's Progressive Association of Latin Americans. Reapportionment after the census should bring a Hispani to the Cook County board, he said.

"When that happens," added Moreno, a state representative from El Paso, about the census and redistricting, "we are going to gain a bunch."

In fixe southwestern states - California, Arizona, New Mexico, Colorado and Texas - Hispanics are the largest mimority, perhaps 7 million of Mexican ancestry. By geography, language, religion, culture and family, they are so joined to Mexico and so influence the dominant Anglo culture that the region is, in many respects, a nation within the nation, and sometimes called MexAmerica.

So in many respects, what is happening with Hispanics here today may only be a prologue to what will happen elsewhere in years to come as their numbers and influence grow.

Even before balloting begins on election day, it is possible, with primary results and other indicators, to tote up the gains and losses for Mexican Americans in this election year.

Some conclusions:

The mumber of Spanish-surmaned members of Congress is not likely to change. There are now five members in the House, none in the Senate. No additional Hispanics were nominated for the House, and the only Senate hopeful, Toney Anaya of New Mexico, is expected to lose handily to Sen. Pete V. Domenici (R.N.M.)

There will be no Hispanic governors next year. By law, New Mexico's Apodaca cannnot succeed himself and his successor, whoever he is, will be an Anglo.

Modest gains have been made in state legislatures in such states as Texas and Arizona. In California, a Mexican-American assemblyman is running for the state Senate and is favored, but his successor in the assembly will be an Anglo.

Local offices held by Mexican Americans will probably increase, despite some setbacks like the removal of Jess Haro from the San Diego council. Primary election victory in Montebello, Calif., means that three of the five council seats there will be held by Mexican Americans.

Such local victories "get the ball rolling" in building orgaiizations and candidates for higher office and thus are crucial, said Al Perez of the Mexican-American Legal Defense and Educational Fund in Washington.

But a victory in Montebello does not overcome the reality of Los Angeles, a city second only to Mexico City in the number of people of Mexican heritage. But there are no Hispanics on the city council.

The reasons for Hispanic inability so far to convert numbers into political power are many - a history threats and discrimination at the polls, low voter registration and turnout and a lack of experience and leadership in many places. In Texas, for example, 850,000 Mexican Americans were either not registered to vote in last spring's primary or were registered but did not vote.

Velasquez notes, too, to that some recent Mexican-American losses of offices have been the result of other sucesses. President Carter appointed Arizona Gov. Raul Castro to an ambassdorship, and three popular local officeholders in Texas were named to substantial federal positions.

Hispanics have been least successful in fielding candidates for, or winning, statewide office, and Apodaca notes that if Mexican Americans are going to be elected statewide they are going to have to campaign on issues appealing to all voters.

Rubin Valdez was expected to become Colorado's first Mexican-American statewide officeholder, but he lost in the Sept. 12 primary for lieutenant governor to Nancy Dick. He had concentrated his campaign on labor and the Hispanic areas of Denver and Pueblo, and had ignored the high-voter-turnout areas of such places as rural eastern Colorado.

Without candidates in statewide races, Mexican Americans are influencing the Anglo hopefuls, and nowhere is that more dramatic than in Texas, where Mexican-American registration has risen 20 percent in two years.

The Southwest voter registration project says that Mexican Americans provided Attorney General Hill with his primary victory margin over Democratic Gov. Dolph Briscoe, who previously had done well in Hispanic areas.

Hill had been responsive to Mexican-Americans' demands for better treatment by law enforcement officers after number of Mexican Americans died while in police custody in Texas.

Now in the general election, Republicans are scrambling to win Hispanic votes, and so keen is the competition in the Senate race that Sen. Edward M. Kennedy (D-Mass.), whose brother, President Kennedy, was revered by Hispanics, has been asked to cut radio plugs in Spanish for use by Texas Democrats, particularly Senate candidate Rep. Bob Krueger.

Perhaps someday the candidates will be Hispanics. Says Ralph Ochoa, chief assistant to California's assembly speaker, Leo McCarthy, "If the Hispanic-Latino communities are gaining more political power, it's because they're getting into the structure, getting close to majority candidates. We have appointments [to office], but not elected representatives.

"Change is inevitablle because of the growing population. We'll get more and more elected officials. Initially, they will be on a local level, mayors, city council. Then they'll be formidable because they'll have apolitical machine and the professionals will put money into those campaigns.

"I see another six years yet before we see some really formidable candidates. Then it wil happen fast. In 10 years, there'll be real change.