The fact is, we don't really know who runs things in Washington. There is a myth that it is the President. But we are approaching another midterm election in which the ''out party'' usually gains House seats (in this case the Democrats) and it will be harder than ever for the President after it to direct affairs because he will probably have less control in Congress.
The odd thing is that the system was planned that way. The Founding Fathers were afraid of George III. They distributed power all over the lot in Washington: they arranged it so that Congress balanced off the President and the Supreme Court balanced off both. Surprisingly enough the system worked. America led the way in reducing the power of monarchs and in increasing the power of voters. But 200 years later we have increasing perplexities. Various scholars have examined the matter; they report that the public is confused. The Congress is more individualistic. The bureaucratic hierarchies have grown; groups of single-minded political activists are moving in. There is lessened faith in the power of the president. There's a ''what's-the-use'' attitude among voters: in the Nov. 2 election probably less than half will bother to vote. That's bad in a democracy.
''By first one means and then another,'' declares Harvard's Hugh Heclo in a recent study, ''we are searching for ways to make our inherited constitutional system, the oldest of existing democracies, cope with modern policy problems that the Founding Fathers could not have envisioned. Summoning up the illusion of presidential government is not much help.''
It has been noticeable in Washington in recent years; it has become a regular cycle: the press building up the presidential rivals; one of them winning election and magnified into a kind of myth; there is tremendous hope in the changes that he will initiate; then he encounters the reality of his obstacles in Washington: a feisty Congress, an obdurate bureaucracy, a reduced discipline in his own party, an increase in special-interest groups. Who is in charge? The country has been able to balance its budget only once in a generation; it has been startled by the revelations of Watergate. Says political scientist John Helmer, ''The electoral cycle presses even more demandingly on the incumbent president now than it used to.''
Yes, I suppose, that's so. It certainly did on Gerald Ford and Jimmy Carter and now Ronald Reagan. Mr. Helmer continues in ''The Illusion of Presidential Government'' (published by Westview Press, Boulder, Colo.) that, ''because his relationship with Congress is uncertain, he (the president must be more sensitive than once might have been necessary to the consequences of his actions for the mid-term congressional election that takes place at the end of the president's second year.
''His own reelection campaign then commences quite early in the third year. By the fourth year, the campaign is at the forefront of his priorities. For only one year, the first for a one-term president, can it be said that he has the time and some political incentive to consider longer-term problems and to make decisions and commitments whose results may not be immediately apparent. But for that period, he must either rely on his predecessor's budget estimates or compose his own budget request in little more than eight weeks after inauguration. . . . In the presidential environment, we might conclude, nothing is ever truly decided, acted upon, done . . . .''
The fact is, Mr. Reagan has been trying since taking office to get a precise budget through Congress and hasn't succeeded. Contrast that with the British Parliament where the government presents its budget and the thing is automatically accepted (short of a national election).
Our system has its virtues, says Lester M. Salamon of the Urban Institute. ''The illusion of presidential government,'' he says in the same collection of essays, ''serves a critical role in our political system, personifying the national will, setting an agenda for national and congressional debate, and providing a focal point for political thinking.''
Maybe so, but he still calls it an ''illusion.'' Mr. Salamon feels that ''the American presidency stands today at a point in its evolution as pivotal as any in its history.'' He adds mildly that the office in recent years has become a source of ''considerable misgivings.''