It is a year of reckoning for voters in Montgomery County.

The 1982 elections there involve much more than voters casting ballots for the party or personalities they prefer. The results will reflect more than a simple acceptance or rejection of Reaganomics, more than the electorate's approval or disapproval of the nation's "conservative swing," more than a determination of the county's political leadership over the next few years.

This year, Montgomery County must make real choices about itself. At issue this year is the county's image, its reputation and a tradition of progressivism in the political process that voters and elected officials have nurtured and clung to for much of the past 15 years.

What is happening in Montgomery is happening elsewhere. It is all part of a new chapter in the political history of America's suburbs, where rapid demographic changes have transformed public institutions and challenged traditional thinking on social issues.

The root of the current identity crisis in Montgomery is quite simple. A decade ago, the county was financially prosperous, and its residents were mostly well educated, mostly middle class and mostly white. Voters could express strong views on social issues--racial integration, housing and civil rights, to name a few --without being confronted in their daily lives by the accompanying social problems.

Although the county's overall population today is largely the same, the arrival of tens of thousands less well educated, less well-to-do, non-white outsiders from foreign countries and the District has altered neighborhoods and schools and social conventions, and caused many one-time "liberals" and old-line "conservatives" to reassess their convictions.

What worries some civic activists in Montgomery is that, as its social profile changes, its reputation for moderation is beginning to fade away. Jewish and minority group leaders are concerned by cross-burnings and incidents of anti-Semitism that have surfaced in many neighborhoods. Traditional "liberals" are worried that a "conservative" school board has irreversibly changed the county's racial integration policies, although the conservatives say their actions are the most up- to-date, practical and "fiscally responsible" ways of coping with hard economic times.

Now, too, the troubled consciences are evident in the electoral campaigns, where new and old philosophies are competing against each other, within the Republican Party and on the school board.

In these two arenas, political ideals nowadays are sold as "pragmatism" and "neo-ism" (which means that as long as what a candidate says sounds new and practical, it should not matter to voters that he or she doesn't have a coherent set of values).

The reserved and moderate officials whom voters in Montgomery once seemed proud to elect have been replaced, in a few notable instances, by individualists who are applauded for their "outspokenness."

Some county residents find the changes a refreshing break from what they believed was a staid and dated political process, and from the procession of bland candidates county voters chose as leaders.

But others are not satisfied, and hark back to the days when county politicking was a quiet, clean and predictable game. Recently, two moderate Republicans legislators resigned from the campaign of congressional candidate Marian L. Greenblatt because they were disquieted by her tactics against incumbent Democratic Rep. Michael D. Barnes. Party leaders explained privately that her claims that Barnes is a "supporter of the PLO" and "a spokesman for the terrorists in Central America" were simply too far out of line in the well-heeled Republican circles of Montgomery County.

Voters casting ballots in the hotly contested school board races -- four of the board's seven seats are up for grabs -- are faced with a raft of issues this year. For example, they must decide whether to support a number of candidates who, among other things, fear that teaching sex education in the eighth grade will "encourage premarital sex" among teen-agers.

The school elections will also be the focus of a continuing and bitter debate over the future course of racial integration in the county's public schools. For the first time since busing became a political issue in the early 1970s, voters will be faced with clear and contrasting alternatives as to the direction the school board should take.

If this hardly sounds like Montgomery County, it is because the political process there is evolving so quickly. Traditional definitions no longer apply, and rules in the political game have changed. No wonder voters feel confused. This year, they are being challenged to sort it all out, and to decide what they want their county's name to stand for in the 1980s.