During last fall's campaign, I found myself on an airplane with a Democratic senator and a Republican Senate aide. We chatted about the campaign, exchanging impressions of states we had visited, weighing the chances of this candidate and that. At the end of the conversation, the Democrat turned to the Republican and said, "Just promise me one thing. Don't give the Senate back to us."

The incident stayed in my mind when the returns showed how close the Democrats had come to recapturing the Senate. The shift of a handful of votes in states like Vermont, Rhode Island, Minnesota, Missouri, Nevada and Virginia would have ended the Republicans' two-year reign.

But what remained even more vivid was the fervor with which this Democratic senator--a liberal and no fan of Ronald Reagan's--had uttered his plea for continued Republican control.

Part of it was pure politics. He said, in so many words, that if the Democrats were given control of the Senate, along with the House of Representatives, then President Reagan would undoubtedly blame the opposition Congress for all the failures and frustrations of the next two years. And Republicans would carry that issue over into the 1984 presidential campaign.

Part of it was an acute and acknowledged sense that the Democrats are not ready, in policy or political terms, to construct their own legislative agenda in Congress.

And part of it, as he said, was the feeling that man for man, in the key spots, the Senate Republicans have better leadership to offer the country than do the Democrats.

That Democratic senator was far from alone. Not since I first came to Washington 27 years ago can I remember a time when the members of one party were so grateful that the other party was running the Senate.

Back then, it was Republicans who were grateful that the Senate was in the hands of Lyndon B. Johnson, rather than the Republican minority leader, William F. Knowland of California. Knowland was bright enough, but a man of enormous pride and unfulfilled ambition, prickly in dealing with both the White House and his own colleagues. Pride and ambition were certainly not alien to Lyndon Johnson, but he had, in addition, a genius for legislative leadership that even his opponents saw was unique.

The same thing is said today by Democrats of Senate Majority Leader Howard Baker. Indeed, it has become almost a clich,e in Washington to describe him as the most effective Senate leader since LBJ.

When Baker went home for Christmas, he was drained and disgusted by the exhausting ordeal of Jesse Helms' and the other right-wing senators' filibuster against the gas tax-highway bill. But, in retrospect, that fight strengthened his position by identifying him, more clearly than ever, as the Senate's leader in a bipartisan sense--getting done the work the Senate's majority wanted to accomplish.

That standing will become even more important in 1983 as Baker leads the Senate in the mission mandated by the 1982 election. It is to set the pragmatic, realistic course of public policy between the polar extremes represented by those doctrinaire septuagenarians, Ronald Reagan and Tip O'Neill. If this country is to be governed the next two years, chances are it will be on terms that Baker and his colleagues define.

No one in American public life has earned and enjoyed a greater increase in prestige and influence in the last two years than Howard Baker. He came out of 1980 a badly defeated presidential contender, untested as majority leader. Today, he is acknowledged and welcomed as the most skilled power broker in Washington.

The change in his standing is mirrored by that of the other two men who share the largest part of his responsibility in economic policy: Finance Committee Chairman Bob Dole (R-Kan.) and Budget Committee Chairman Pete Domenici (R-N.M.).

In two years, Dole has utterly outgrown his previous reputation as a petty partisan and failed national candidate, to gain respect as an independent-minded, highly effective and often courageous legislator with a very broad view of the public interest.

Domenici, the least known of the three two years ago, overshadowed even on the Budget Committee by Sen. Henry Bellmon (R-Okla.), who retired in 1980, has turned out to be a godsend: a serious, hard-working, well-staffed senator, with a realistic and thoroughly non-doctrinaire approach to his job.

This is going to be a tough year for Congress--and the country. But when the liberal organization, Americans for Democratic Action, derides the Senate majority, as it did, as the president's "marionettes," it is as off-base as it was when it was saying the same things about LBJ, 25 years ago.

The country knows better--and so do the Senate Democrats