A decade ago a state senator named John Schmitz, whose conservatism was exceeded only by his sense of humor, quipped he had joined the John Birch Society because he "had to do something to get the middle-of-the-road vote in Orange County."

Schmitz, who now teaches political science at Santa Ana College, understood his constituents. In the rise of the right that was one of the features of political life in the 1960s, Orange County was a pioneer.

The county supported every fashionable conservative cause and candidate. It was a bastion for Barry Goldwater and Ronald Reagan and for initiatives that would have outlawed obscenity and imposed antisubversive controls.

These measures and candidates except for Reagan were overwhelmingly rejected by Californians, but they carried big in Orange County. After all, it was the home of the Santa Ana Register, which routinely editorialized against spending public funds even for schools or jails.

Nationally, "Orange County" became a symbol for some of the kookier varieties of conservatism.

Democrats, with few exceptions, were inclined to write Orange County off as a lost cause in the 1960s. The only credit the county earned from its Democratic and liberal detractors was that its politics generally were ethical and aboveboard, without hint of corruption.

Now, after a period of tumultuous growth in which the county's population has increased from 700,000 in 1960 to 1.8 million today, the Orange County reputation for conservatism is tattered and so is its record of integrity.

With some significant exceptions, the ideologues of the past have been replaced by indistinguishable unprogrammatic politicians of the present. And the tradition of good government has been engulfed by 43 indictments of public officials during the last three years on such charges as bribery, theft, false voter registration, perjury and laundering of campaign funds.

The list of those indicted includes two congressmen, three supervisors and the county assessor. Thirty-six of those indicted have been convicted or have pleaded guilty. Only one has been acquitted. The rest are awaiting trial.

What happened to the twin Orange County traditions of conservatism and incorruptibility? The answers, as to so many questions in California, are bound up in the land.

A decade ago Orange County was a rural, bedroom community of pretty fields and orchards mixed with tree-shaded inland towns and attractive coastal communities. Today it is the fastest growing and 19th largest metropolitan region in the nation, and the second most populous county in California. It lies at the center of the developing San Diego-to-Santa Barbara megalopolis.

Most of the orchards that gave the county its name have been torn down to make way for tract houses. In the process, millions of dollars have changed hands, mostly as the result of zoning decisions made by the county board of supervisors, which controls development of unincorporated land.

"If you get to be a supervisor in Orange County, you get to zone the fastest growing part of the country," Schmitz said. "There's a kind of legalized extortion you can perform.

"If you throw a $1,000 cocktail party, are the land developers going to come? You bet your sweet Aunt Molly they are. You've got to be virtually a St. Thomas More to be [an honest] supervisor."

In other fast-growing regions of the West, county officials often have been restrained by the competing demands of a developed central city. There is no such city in Orange County.

"While exploding with growth, Orange County became 26 cities in search of an identity," wrote Bud Lembke in California Journal. "Downtown Santa Ana deteriorated, its stores unable to compete with outlying shopping centers.

"The county lost its focal point. Its two most prominent features today are probably the ersatz Matterhorn at Disneyland and Anaheim Stadium . . . neither quite fills the bill as a rallying point for suburbia."

The lack of centralism is reinforced by the absence of a single dominating newspaper or television station. Much as New Jersey is overshadowed by the concerns of New York and Philadelphia, Orange County is outshone by the glow of Los Angeles, where the television stations rarely bother with Orange County issues.

A random poll by the Los Angeles Times of 100 persons at Orange County shopping centers showed 49 of them had never heard of the 43 indictments, despite heavy newspaper coverage.

State Controller Kenneth Cory, a rare Democratic state assemblyman in the days when the county was represented mostly by Republicans, thinks two factors contributed to and then undermined deep conservatism in the county.

First, Cory believes, was the appeal of "new right" doctrines to the "absolutism" of the many aerospace engineers who made their homes there. But then came the aerospace economic slump of 1969 and 1970, forcing these engineers to seek federal help and making government intervention seem more benign.

"Suddenly, it was their families who needed welfare, not the 'welfare chiselers' they have been talking about," Cory said. "And it was they who were on unemployment and wanted it extended."

The population growth brought into Orange County huge numbers of people who knew little or cared less about the county's conservative political tradition.

These included suburban liberals, some Mexican Americans and academics associated with the growth of University of California-Irvine.

In California newcomers can have an impact in a hurry. Within a short time the new Orange County residents were beginning to alter fundamentally the character of such important institutions as the county grand jury, which under California law has widespread investigatory authority.

"The grand jury on which I served in 1969 had two blacks, two Mexican Americans, five women, four Jews and seven or eight Democrats," said Judy B. Rosener, a writer on the staff of public administration at UC-Irvine.

"It was disproportionate to the county. The grand jury asked questions. At the same time the county was developing, you had a group of people who were questioning development."

The grand juries also were questioning - and ultimately indicting - some of the candidates who received huge sums of money from developers and paid it to campaign firms that relied heavily on computerized mailings and misrepresentations of opponents' campaign statements bordering on "dirty tricks."

"The average candidate will do anything to win an election," said Arnold Forde, one of the most successful campaign managers in the county.

A majority of those indicted were Democrats. Such goings-on led Frank Mesple, a lobbyist who was a principal aide in the state-wide administration of Gov. Edmund G. (Pat) Brown, to crack, "You guys are indicting Democrats as fast as we can elect them."

A number of Republicans also bit the dust, including Rep. Andrew Hinshaw, who with support from the Nixon White House defeated Schmitz in the 1972 congressional primary.

Schmitz provided Hinshaw with the political ammunition in the form of a quip that he "didn't mind Richard Nixon going to Red China, but just didn't want him coming back."

However, the troops for working the precincts came from the office of Hinshaw, who was then the county assessor. Nine aides were indicted or convicted after the election, and Hinshaw himself ultimately was convicted of bribery and defeated by the voters in 1976.

Orange County today remains a Republican county, but with a Democratic core. The central area of Santa Ana, Garden Grove and Buena Vista has a Democratic representative in Congress and three Democratic state legislators.

Otherwise, the county hasn't changed its conservative outlook as much as some people like to think. Its other two congressmen, Charles Wiggins and Bob Badham, are conservative Republicans. The GOP holds a 4-to-2 edge among state legislators in these districts, and five of the legislators are conservatives.

And Schmitz, who has won eight elections and lost two in the county, is running for a soon-to-be vacated state Senate seat in a race where conservatism is taken for granted.

Even so, the candidates in this race are talking not about the John Birch Society or "welfare chiselers" but about who will do the best job representing the county in Sacramento.

While the county may still be the most conservative in the state, as Schmitz contends, the old fire-in-the-belly passions that stirred the "new right" seem to have been lost among the vanquished orchards.