`Third force' in disarray

DAVID OWEN, who came away from the British elections in June as a party leader without a party, is now no longer a leader at all. Mr. Owen, once touted as a future prime minister, has resigned as leader of the Social Democratic Party after a party vote favoring a merger with the Liberal Party. Owen has opposed the merger, and so felt it inappropriate for him to lead his party as it negotiates with the Liberals. The process should take until spring, and will require a two-thirds majority vote of the SDP policymaking council.

The two parties - the Social Democrats, founded in 1981 by the ``gang of four,'' who broke away from the Labour Party, and the much-older Liberals - had in fact been cooperating under the name of ``the Alliance.'' But many voters were confused as to what the Alliance stood for, and in fact the two parties have not only very different histories but very different policies - notably on defense: The Social Democrats have favored retention of Britain's independent nuclear force; the Liberals have endorsed disarmament.

And Owen has been unwilling to submerge his hopes of occupying 10 Downing Street to those of Liberal leader David Steel, whose party holds 17 of the 22 Alliance seats at Westminster.

A merger would presumably make of two very small parties, one small party, whose best hope would be to hold the balance of power between Conservatives and Labour. That hope has already been dashed once, in June, when Prime Minister Margaret Thatcher was able to hang on to a reduced but still absolute majority in the Commons. With only five seats in the Commons, the Social Democrats felt a need to do something. But it's not clear that the product of an SDP/Liberal merger is going to seem less confusing to voters than did the Alliance in June.

The SDP's launching in 1981 raised hopes of a new centrist ``third force'' in British politics; now that all seems in doubt. If the Social Democrats and the Liberals cannot make it as an alliance, how are they to make it as a party?