A "new" idea about Soviet-American relations is gaining some currency. It is a telling symptom of the new possibilities in Soviet policy that some Soviets hope, and some Americans fear, have been opened by the ascent of Mikhail Gorbachev.

The idea is that there are in effect two foreign-policy parties in the Soviet Union, an America party and a Europe party; that former foreign minister Andrei Gromyko represented the first and new Communist Party General Secretary Gorbachev represents the second; and that unless the United States becomes more accommodating, Soviet policy will turn away from Washington and instead concentrate on Western Europe.

Now, I grant that this is not nearly as catchy as the report that Raisa Gorbachev was recently seen on television wearing no fewer than three different and stylish outfits during one day with her husband at Dnepropetrovsk. But as Ronald Reagan's first summit with Mikhail Gorbachev in November nears, all of us are going to have to pay attention to the more mundane facets of Kremlin life.

The first facet is, as usual, the configuration of power on the inside. A good many observers have already proclaimed Gorbachev the unchallenged king of the Kremlin hill. But has he earned it? He gave a speech in Leningrad last month which, he said, he edited himself for television. A later printed version removed both his praise for East German economic reform and his criticism of the Politburo for failing to approve more than a million private backyard plots for collective farmers. Who's his editor? Your true Kremlinologist is one who finds this more intriguing than Raisa's wardrobe -- almost.

So the question of Gorbachev's actual independent operating authority hovers over any inquiry into nuances that may exist or emerge between him and his Politburo colleagues.

The notion of Moscow's playing a Europe card is, of course, familiar. The recent accent on it came first, so far as I am aware, in suggestions passed on to The Post's Moscow correspondent, Dusko Doder, when Gromyo was kicked upstairs to the Soviet presidency. Others have since elaborated on the theme. The basic thought is simply that Gromyko had long been associated with relations with Washington, that these relations aren't going very well, and that Moscow can take up the slack with Western Europe.

The Soviets who brought this up were surely pitching a curve in the hope of making Americans a bit more eager to offer concessions at Geneva. Very few Soviet analyses end in the conclusion that it is the Kremlin's course that must change.

But as you think about it, the Soviet Union no more has a Europe card than the United States has had a China card. In both cases there is good reason for the great power to improve ties with the third party, but the emphasis must necessarily remain on great-power relations themselves. Why? Only the United States and the Soviet Union have a world reach and pose a mortal threat to each other.

The Soviets have spent the past 40 years trying to weaken Atlantic ties; Gromyko, the supposed Americanist, never stinted this line. The United States, getting a late start, has spent the past 10 years trying to weaken Sino-Soviet ties. But both great powers surely understand the limitations of this line of policy.

Gorbachev is probably no more disposed than any of his comrades or predecessors to put all of Moscow's eggs in an American basket. The enduring issue of interior Kremlin debate, it has always seemed to me, is not whether to play the Europe card, which is not that much of a card, or whether to go it alone, which is not a real option in the modern world, but how much political capital to put at risk at any given moment in re- lations with the United States. Gorbachev is playing it close to the vest.

There are, however, signs that the Kremlin is even now testing Ronald Reagan's second-term intentions. These signs are not seen everywhere, or at least they are not similarly interpreted everywhere, within the U.S. government. But some see small movement surfacing at all three Soviet-American negotiating tables at Geneva. In these crucial matters of strategic arms, the Soviet Union has no negotiating partner other than the United States.