It was one of those great turns in US history -- but how far?

An American public that had been called indecisive and apathetic acted with firmness -- if not fury -- when its turn came in the voting booth. It was a vote for optimism, historians may later observe, a drawing of the line against economic stagnation at home and humiliation abroad.

"Enough," the voters said. "America can do better."

So broadly did the sweep carry -- from the Reagan landslide, to the US Senate , to the state capitals -- that it must have been more than just repudiation of a sitting president, observers say.

An ideological drift may be occurring that is conservative in nature and southwestern in direction.

Looking ahead, the industrial states of New York, Ohio, Illinois, Michigan, and Pennsylvania will lose House seats and Electoral College votes starting in 1982. The gainers will be conservative states like Texas, California, Arizona, and Tennessee, as well as Florida, Oregon, and Washington.

Put another way, the "frost belt" Electoral College votes outnumbered Sunbelt votes by 41 when Democrat John Kennedy won in 1960. But for the Carter-Reagan election the Sunbelt led by 4. In the 1984 election, the Sunbelt will lead by 26, say elections experts Richard Scammon and Ben Wattenberg.

The 1980 election appears to have embedded other lasting trends as well.

The apparent success of conservative and single-issue groups that targeted liberal senators for defeat suggests more such political citizen-posse actions in future elections. More independent committee support for presidential candidates will likely also be seen.

The limited success of John Anderson's independent effort revealed that the American electorate is still drawn to the basic Democratic and Republican poles. That may discourage more such independent attempts in the future.

In terms of party organization, the Republican National Committee under chairman Bill Brock so decisively forged a united presidential, Senate-House, and state party effort that the Democrats will have to attempt the same unified approach in the campaigns ahead. The Democrats submerged their national party machine in the President's re-election effort; the Republicans invested effectively in recruiting talent and making the best of their minority-party ranks. Organizationally, the Republicans are in vastly better shape to run again.

Ideologically, Democrats who survived the 1980 election say there has been erosion of their policy base as well as their power base.

Younger Democrats know that neither adopting the New Deal policies of their seniors -- such as wage-price-control intervention -- nor aping the "supply side" economics of their GOP competitors will suffice for the 1980s. Some of the younger Democrats envision the need to amass huge amounts of capital, under government aegis, to modernize American industry. But the convincing Republican 1980 victory suggests a half-decade at least of experimenting with GOP economic theories before the Democrats can again mount an innovative counterforce of their own.

On social issues, the results suggest further coolness, if not a freeze, for the "class rights" struggles of the '60s and '70s, including women's rights, at the federal level -- as in the Equal Rights Amendment and abortion funding. The Reagan election and related conservative gains elsewhere reinforce a gathering trend to the support of individual rights against class rights.

The individual's right to earn his way up the ladder, to invest as he sees advantageous, will be given greater weight against the demands for support of an underclass -- such as minorities -- political historians say. Such Reaganesque phrases as "getting government off our backs" and "let's unleash American industry" reflect the trend toward "individual freedom" now apparently ascendent on the American political scene.

The broad Democratic "equality" concerns of unions, ethnic groups, blacks, and religious minorities like Jews and Catholics seem to have been further muted in this election. Sen. Edward Kennedy's failed attempt to awaken and reforge these groups during the primaries, like President Carter's in his frantic late-campaign drive, likewise point to the end of an era.

Conservative emphasis on individual rights vs. liberal emphasis on group equality represents a broad dynamic of American politics going back to the nation's founding, political historians say.

What Americans may have seen this week was another tipping of the cycle.

However, Republicans could make two serious mistakes in misreading the signs of the times, analysts warn:

* The weakening of Democratic coalition ties may not mean any permanent realignment of these groups.

Instead, argues University of Connecticut political scientist Everett Ladd, the United States may be entering a period of "de-alignment." "Americans, more educated and more leisured, have become permanently less inclined to defer to party leaders and more inclined to vote independently," he says.

The other side of the individualism coin is that Americans are getting harder to lead. The Republicans must refight their battle for electoral control in every coming election.

* Americans are in no mood to have the liberal gains of the past two decades repealed.

Greater military spending and assertion of American power abroad will likely be seen in an emerging Republican era, experts suggest. But any attack on "the welfare state" or the unions would likely end a GOP era instantly.

Many of the recent social changes, such as those legalizing abortion, are rooted in the individual's right of decision against intrusion by the state -- the very point conservatives are stressing in economic and other policy. Right-wing attempts to impose "moral majority" will in civil liberties areas would likely cost Republicans the moderate backing that convincingly tipped the scales their way this Nov. 4.