Time for coalition government?

Things are coming to a head here in Washington. Congress returns Monday. The President delivers his State of the Union address Wednesday. He will announce on Jan. 29 whether he will run for a second term. He celebrates his 74th birthday Feb. 6 and shortly afterward flies to China for a goodwill visit.

Temporarily, at least, the economy looks better. Unemployment has dropped from a high of 10.7 percent down to only around 8 percent. That's still too high , of course, but still there are 4 million more jobs. On the foreign affairs front Mr. Reagan has not denounced the Russians recently. Nobody here wants to defend them, but it's questionable whether it is wise for the leader of one superpower to call the other an ''evil empire.'' On the business recovery side, Mr. Reagan and Congress have created a federal deficit of around $200 billion a year, and the end is not in sight. If Mr. Reagan runs again and wins (which he's apt to), he will face bitter problems. At election day in 1980 things were less hectic. If perchance Reagan does not seek reelection, there will likely be a place for him as an elder statesman.

Choosing the American president is of world interest. The well-edited London Economist asks on its Jan. 13 cover, ''Should Reagan run?'' It doesn't answer; it would be cheeky if it did. Apparently it wants to emphasize how important this moment is; that neither Mr. Reagan nor the American public should delude themselves that gigantic decisions are imminent. Also that the new term isn't likely to be like the last, that Mr. Reagan has created a firm international stance for bargaining with Russia and that he had better not take on a second term unless he is prepared for crucial problems. In short, ''Faced by a more Democratic Congress than before, an administration of individuals will become one of chaos unless Mr. Reagan decides to exercise his own authority at an earlier stage of policymaking than before.'' Well, maybe yes or no. But tension increases.

There comes across the desk a book by Theodore C. Sorensen, an international lawyer and former chief aide to President Kennedy, entitled ''A Different Kind of Presidency.'' Mr. Sorensen recommends a temporary coalition government, similar to that used in European countries in moments of crisis. In 1910, he recalls, young David Lloyd George urged a political coalition on Prime Minister Herbert Asquith (which the latter rejected), but there were war cabinets later. Franklin Roosevelt took prominent Republicans into the government in the war. Not to mention Abraham Lincoln, who picked Democrat Andrew Johnson to run with him in the Civil War.

How do you have a coalition government in America with our unique system of separated powers and rigid written Constitution? Mr. Sorensen has a technical answer, which isn't likely to be accepted but which illustrates the nation's considerable concern.

In brief he proposes a one-term, bipartisan coalition government of ''national unity.'' President and vice-president would be of opposite parties, each agreeing in advance to serve one term and decline all partisan activities. Also, cabinet and subcabinet would be equally divided between parties; there would be a small bipartisan White House staff; a presidential advisory council of ''Elder Statesmen''; a national Council of Economic Cooperation; ''a joint Executive-Congressional delegation to the US-USSR arms reduction talks''; and, finally, a return to politics as usual at the end of four years!

Unconstitutional? Not, Mr. Sorensen argues, if customary forms were followed. (Political parties are not recognized in the Constitution.)

A coalition government in America? It's not likely to be accepted. But something needs to be done. And Sorensen says, ''If it can be given a formal structure, officially established, organized on a continuing basis in the White House itself, and shielded from partisan exploitation, a bipartisan Coalition Government for one crucial four-year period could change, as was said of the Andrew Johnson vice-presidential nomination, 'the destiny of the country itself.' ''