THE old adage has it that partisan politics stops at the water's edge, but the water's edge is fast disappearing under the Republican wave.
In Jakarta this week, President Clinton reassured Asian leaders that he still has the constitutional responsibility for the conduct of foreign policy.
But Mr. Clinton - pardon the expression - is whistling Dixie. The Republican majority, starting with Jesse Helms, the next chairman of the Senate Foreign Relations Committee, is staking out foreign-policy positions that can be disruptive to the administration's plans. The early articulation of these positions is already casting a menacing shadow.
Senator Helms will not be another Arthur Vandenberg, the champion of bipartisan foreign policy. The Michigan isolationist, converted to internationalism by the experience of Pearl Harbor, cooperated with President Truman in his principal foreign-policy enterprises, such as the Marshall Plan, NATO, and containment of the Soviet Union.
But times are different, and so is Helms. In the breathless days since the midterm election, he has asserted these positions, among others:
* Opposition to joining in United Nations peacekeeping missions, which he says obstructs American purposes and costs billions of dollars.
* Opposition to most foreign aid, which he says has sunk $2 trillion down ``foreign rat holes'' to countries that often oppose the United States.
* Reservations about the Middle East peace process, especially softness on Syria and any plan to station American troops on the Golan Heights.
On top of this, Sen. Robert Dole, the next majority leader, has called for pulling US troops out of Haiti by Thanksgiving; Republicans are questioning a decision to provide nuclear reactors to North Korea (just at the moment when China has agreed to support that arrangement); and Republicans believe Clinton has been too friendly to Russia. Add to this signs of protectionist trade sentiments among the new crop of populist congressional Republicans and it is easy to understand why Clinton found himself facing worried Asian leaders' questions.
``I don't expect the election to have any impact on our foreign policy,'' the president said at his news conference in Manila on Sunday. But foreign officials know when a president has been seriously weakened. They also know what an assertive Congress with the power of the purse, treaty ratification, and confirmation of diplomats can do to reduce a foreign policy to shambles.
The question is whether the triumphant Republicans fully realize that they are no longer the opposition just sounding off, but what they say counts. The Opinion/Essay Page welcomes manuscripts. Authors of articles we accept will be notified by telephone. Authors of articles not accepted will be notified by postcard. Send manuscripts by mail to Opinions/Essays, One Norway Street, Boston, MA 02115, by fax to 617 -450-2317, or by Internet E-mail to OPED@RACHEL.CSPS.COM.