Finally President Reagan has pointed the way to every president's goal of a bipartisan foreign policy. It's not that his own policy has achieved that sublime status, but he will leave the country a policy that is considerably less off-center and divisive than both the one he ran against in 1980 and the one he himself then installed.

This result has come gradually, but its progress has been greatly accelerated by three events of the summer. The first was Reagan's decision to take Democratic House Speaker Jim Wright as a partner in Central America. The choice did not give the president a fully wrought bipartisan stand, let alone one assured of success. But it did put him in tentatively bipartisan company on the single most contentious issue of the postwar period: the issue of intervening in a foreign country in order to block a communist opportunity or to advance an American one. He decided to give some extra space to a new diplomatic approach.

Just this week, Reagan moved on to consolidate bipartisanship in arms control, the arena of high policy in which the strategic relationship with the Soviet Union is most vividly acted out. He adjusted the American position on verification in a proposed treaty limiting intermediate-range nuclear weapons. His earlier position had been based on the ideologically congenial premise of total distrust of the Soviets. The new one is designed to ensure the kind of verification consistent with achieving an agreement otherwise in the American interest.

But not all the movement toward bipartisanship has been by the president. This summer the Democrats in Congress, more or less despite themselves, have gone that way on what is, after Third World intervention and strategic arms control, the third-great issue of American policy: use of force in hot spots.

Jimmy Carter had begun by formally raising the official valuation of the American stake in the Persian Gulf to the level of ''vital'': vital means it's worth defending. The current Congress confirmed the movement by endorsing in its fashion -- with many misgivings -- the president's naval policy in the Gulf. Even those Democrats who favor invoking the Vietnam-era War Powers Act, the law designed to check presidential initiative, make clear that most of them seek not so much to confront the president as to support him.

Suddenly, then, the United States has the makings of a bipartisan foreign policy. The president and Congress got to it inadvertently and by different routes. It has mattered to the White House, for instance, that the Iran-contra affair has taken its toll on the president's standing and that Mikhail Gorbachev is coming on strong. It has mattered to the Democrats that they tend to lose presidential elections.

But perhaps the most important thing is that just as Jimmy Carter had enough time in office to reveal the pluses and minuses of a policy oriented toward the left, so Ronald Reagan has had even more time to test and display a policy oriented toward the right. The turn toward the middle, in short, arises from experience extensive, varied and recent enough to make it politically valid.

Those who seek additional evidence of the turn need only observe how some of the president's most loyal followers are writhing in agony to see him moving to rejoin the mainstream whose earlier abandonment by Reagan had been the cause of their rejoicing. Probably it's foolish to underestimate their bitterness and their readiness to undercut the latter-day Reagan, although -- to confess -- it's kind of fun to see the long faces.

It is always good news to find a bit of reality breaking through -- especially now in the presidential campaign. The early phases of the nominating process are often said to be captive to the more extreme folks of both parties. True or not, Democrats are tending to bunch toward the center, and where Jack Kemp and a few others are cultivating the part of the Republican spectrum that supported Reagan in his prime, the heavier Republican hitters are in a place that many Democrats could live with.

I don't mean to suggest that passion, venom, individual nuance or, least of all, the capacity for grievous error have gone out of the making of foreign policy. There's political company in the center, but whether there's wisdom and sureness is another matter. Company, however, is worth a lot in this business.