Before the "conservative tide" of 1980 becomes permanently fixed in conventional wisdom, some of the finer print from last week's election returns deserves srutiny. Conservatives were the biggest winners this year, but not the only winners -- a lot of moderate and liberal Democrats prevailed, too.

In Senate races, for example, certifiably progressive Democrats won big victories in states as diverse as Connecticut, California, Arkansas and Ohio. The only Democratic senator in the history of the state of Vermont -- a liberal -- won reelection. Twelve sitting Democratic senators did lose this year, but a careful look at the list suggests that few of them can be described merely as victims of a national conservative tide.

The results of Senate races this year -- as in 1978, when the Democrats lost three seats -- suggest that factors other than simple ideology are working against the party that has dominated Congress for 50 years. If ideology alone were the explanation, few of the 12 Democrats who won Nov. 4 could have done so; but if the Democrats didn't have serious problems with the voters, they'd still enjoy the overwhelming strength they had in the Senate before 1978.

The defeated Democrats of 1980 can be divided into three basic categories. First, the well-known liberal leaders: Birch Bayh (Ind.), Frank Church (Idaho), John C. Culver (Iowa) and George S. McGovern (S.D.), all of whom come from states that had seemed unlikely homes for liberals in the first place -- conservative states whose other senators are Republicans. All four of them were expected to have trouble this year.

Of these four only Church lost narrowly -- by just 4,400 votes. The other three were beaten decisively by well-financed and prepared conservative candidates, all of them members of the House. McGovern and Church had been palpably out of step for years with their conservative western constituencies on many issues. Bayh's three previous races had all been extremely close in a state dominated by the Republicans.

All four of these liberals had plenty of money this year, but money could not overcome voter resentment against the state of the nation.

When liberals like these had good issues to run on, they had a fighting chance to win election from these Republican states. But there were few good issues for them this year; they were the ins -- longtime ins at that -- at a time of economic distress and international troubles that naturally favored the outs. They had no Vietnam war to mobilize their supporters, no Richard Nixon to demoralize the opposition, no natural advantages at all.

A second group of defeated Democrats were senators of indifferent reputation who had failed to make a strong mark either in Washington or at home. Among them were John A. Durkin (N.H.), a labor-backed liberal from conservative New Hampshire; Robert Morgan (N.C.); Mike Gravel (Alaska), who lost in the Democratic primary to Clark Gruening, who could not fight a Reagan tidal wave in his state; Donald Stewart (Ala.), also defeated in a primary by Jim Folsom Jr.; Richard Stone (Fla.), defeated in a primary.

Politicians on Capitol Hill and in their home states predicted trouble for all of these men except perhaps Morgan, who, as a former state attorney general, was thought to have a wide following despite his lackluster performance as a senator.

A third group of defeated Democrats consisted of senior members whose constituents seemed to conclude that their time had passed: Warren G. Magnuson (Wash.), a man with a fondness for whiskey who showed his 75 years; Herman Talmadge, 67, an admitted alcoholic who had been "condemned" by his Senate colleagues for financial misconduct; and Gaylord Nelson, 64, beloved by his Senate colleagues but known in Wisconsin as out of touch and insufficiently attentive to his political pastures at home.

Two other sitting Democratic senators chose not to run this year: Abraham Ribicoff (Conn.) and Adlai E. Stevenson (Ill.) In both states, Democrats were easily elected to succeed them, suggesting that it was a boon this year to be a newcomer, no matter what your party identification.

With all the anti-incumbent sentiment in the land, though, 10 Democrats won reelection, most of them handily. Alan Cranston, blessed with a feeble opponent, won in California by a 3-to-2 ratio, while Reagan was carrying the state by almost as much. John Glenn won a 70-to-30 victory in Ohio. Gary Hart and Thomas F. Eagleton won closer races in Colorado and Missouri. Ernest F. (Fritz) Hollings, liberal on many domestic issues, won a huge victory in South Carolina, as did Wendell Ford in Kentucky. Dale Bumpers, one of the most articulate progressive in the Senate, was reelected in Arkansas with a 20-point margin.Daniel K. Inouye won in Hawaii, and Russell Long won without any opposition in Louisiana. Patrick J. Leahy, Vermont's first Democratic senator, was narrowly reelected while his state's Republican governor won handily and Reagan defeated Carter.

Reagan won every one of those states except Hawaii.

Until a few years ago, incumbency was regarded as a great advantage in running for the Senate. Arguably it has become a disadvantage. Polls have shown a steady increase in public frustration with Congress, a frustration that seems easier to vent on more remote, majestic figures in the Senate than on hometown members of the House of Representatives.

Moreover, Democratic candidates this year had no coherent political program. "The Democratic Party did not present anything that was different," as Peter Hart put it. Hart, a pollster and political consultant who worked with 11 Democratic candidates for the Senate this year, had predicted for nearly two years that the Democrats would suffer serious setbacks in 1980. "We were presenting individual cases against the Republican Party . . . and they had a unified message which came from top to bottom," Hart observed.

As long as Democrats outnumbered Republicans in the Senate, the disadvantages of incumbency had to favor the Republicans. But the game has changed; now it is the Republicans who will be held responsible for the course domestic and foreign affairs, and the Democrats will enjoy the fun of running as the outs who needn't take responsibility for the follies of the ins.