THE DEMOCRATS have begun behaving lately in a manner that may foreshadow either a genuine revival or--at the least--what party loyalists pardonably might consider a reasonable facsimile. Their recent experience, it should be said, reflects the normal rhythms of American political culture. When a national party has been shellacked in a presidential election, more often than not, first the victors and soon the professional coroners of American politics post its death notices if only to ponder them out loud. Americans have been assured confidently by experts during the past half-century, for example, that the unseated Republicans of 1932 (and again of 1964 and 1976) would soon self-destruct in the manner of the previous century's Federalists and Whigs. Nor have similar prophecies been lacking about those "emerging Republican majorities" seen on the horizon after Democratic debacles in 1952, 1972 and--most recently--1980.

Although still waiting for the American public's personal affection for Ronald Reagan to decline (a necessary precondition for any revival of Democratic fortunes) party activists appear noticeably less demoralized--and more determined--than during the "Democratic Dunkirk" of Mr. Reagan's budget and tax victories. In this connection, House Democrats acted wisely when they resisted demands from within the caucus to punish immediately those who voted for the Reagan program, presumably by stripping them of leadership posts or seniority. At the same time, the Democratic caucus made it clear that future defectors will be shown less mercy, so any closet Reaganites in the party confront the prospect of swift--and painful--party discipline if they support the president against their own commanders in the coming months.

The reconstruction of Democratic national political machinery has also been proceeding more smoothly than some had predicted. Again, this fact has precedents in earlier electoral debacles. This week, the Democrats set the ground rules of their 1982 mid-term meeting without an overt display of squabbling between congressional leaders and Democratic National Committee figures. The current atmosphere of intra-party harmony may not survive, of course, the emergence next year of the major--if undeclared--presidential candidates for '84. Nor should much reliance be placed on the Democrats' own recent avowals that new blood, newer ideas and the newest of spirits have begun sprouting already in their barely weeded political garden. For one thing, we do not know at this point whether the party's legislative strategists will prove any more skillful than they were last time at holding the rank and file in place, especially in the House, to oppose The Great Persuader's forthcoming "supplemental" budget slashes.

Now that post-election May has turned into pre-election September, all that seems apparent is that the reports of terminal partisan illness--though encrusted with tradition by now as an expectable response to the aftermath of defeat--seem as premature as they proved to be in the past.