What with one thing and another -- the Falklands, El Salvador and a rising tide of trouble and tension in U.S. relations with Latin America--this Sunday's election in the Dominican Republic may have escaped your notice.

But if power changes hands in a more or less orderly way, it will be a noteworthy event, a triumph for democracy in a corner of the world not famous for peacefully handing over the controls from one government to the next. And it could be more than merely noteworthy, if things turn out as badly as they have had a habit of doing over the Dominican Republic's long, tortured history of violent upheavals, military coups, brutal tyranny--and American diplomatic and military intervention.

Either way, the likely outcome of the voting promises to provide a stress test of the integrity and credibility of Ronald Reagan's Latin American policy. The Dominican Republic has had a way of doing that to American presidents. In a manner all out of proportion to its size, it has profoundly involved the United States in its affairs since U.S. Marines first occupied it early in this century.

When the 30-year dictatorship of Rafael Trujillo ended in a hail of bullets in 1961, John F. Kennedy, who was thought to be a liberal fellow in these matters, propounded a policy that would warm the heart of the most ardent Reaganite.

Kennedy examined the situation "realistically," Arthur M. Schlesinger Jr., wrote in "A Thousand Days," and concluded: "There are three possibilities in descending order of preference: a decent democratic regime, a continuation of the Trujillo regime or a Castro regime. We ought to aim at the first, but we really can't renounce the second until we are sure that we can avoid the third."

That hard-nosed attitude carried over to his successor. Lyndon Johnson sent in U.S. Marines and the 82nd Airborne Division when he sensed, on the slimmest of evidence, a possibility that a violent upheaval and almost total anarchy in April 1965 might bring communists to power and create "another Cuba."

Things took a turn for the better when, for the first time in its history, the Dominican Republic actually carried off an orderly transfer of power by the election of Antonio Guzman as president in 1978. But only heavy intervention by Jimmy Carter kept the military from stealing the victory.

Guzman engineered welcome political reforms. But he is honoring his pledge to step down after one term, which sets up the test for Ronald Reagan on Sunday under conditions remarkably comparable to those that confronted Carter four years ago.

The odds-on presidential favorite is a 55-year-old lawyer, Salvador Jorge Blanco, a member of Guzman's Revolutionary Democratic Party. He is essentially a social democrat, leftish but held by the State Department to be untainted by the sort of Marxist-Leninist inclinations that are fatal to any foreigner seeking Reagan's favor.

He has, in the delicate words of one U.S. expert, a number of supporters "with a troublesome past"--meaning some degree of communist connection --that the State Department would just as soon not have wind up in a Blanco government. But the official line is that the Reagan administration is "prepared to work with any government elected in a free and fair election."

That is not necessarily the view of important hard-right elements in the Dominican military and police forces. True to their thuggish tradition, they are already making ominous noises, warning of swarms of communists ready to infiltrate the government if Blanco wins.

The official U.S. response is firm: repeatedly the State Department has let it be known that it would "view with great disfavor any interference with the election results." At the very least, that sounds like a clear signal that the Reagan administration would not avert its gaze if the Dominican military moved to nullify a Blanco victory.

But in some quarters in an administration dedicated tothe proposition that authoritarian regimes are preferable to totalitarian (Communist) regimes, the rumblings from the hard- rightists in the Dominican military may well have found a sympathetic ear. There is some danger, in short, that the official signs of "disfavor" may have been scrambled by contrary, unofficial signals of encouragement from, among other sources, the Pentagon, where there is a natural affinity with the Dominican military.

So it may take more than expressions of "disfavor" to keep the voting honest. It may take the sort of diplomatic muscle the Carter administration applied four years ago. The question worrying some observers here is whether the Reagan administration, by its nature, is prepared to go that far.