FANS OF THE Washington Senators are quietly ecstatic over their team's capture of the American League pennant, and bubbling with enthusiasm at the thought of its appearance in the World Series, which begins this weekend. When we speak of Senators' fans, of course, we mean that steadfast band of legitimists who still recognize as their true home team the one that last played in this city when Dwight Eisenhower was president, in a stadium that now exists only in fond memory.

Unlike those who protest old injustices and seek to right them, such fans simply refuse to recognize that the injustices ever occurred. Like the monarchist who still drinks a nightly toast to the continued rule of the Hapsburgs, Bourbons and Hohenzollerns, the true Senators fan doggedly attempts to tune in his team on the radio every evening from April through September, curses the poor reception that thwarts his efforts and fully intends to get out to the park more often, although he has had some trouble finding it for the past 20 years or so.

The most that some will acknowledge is that the Senators have been on an extended road trip, apparently as part of an experiment by misguided heirs of the late Clark Griffith to see whether major-league baseball could be played in extreme northern climates. To Senators' fans, the absurdity of this experiment became apparent a few years ago when the thoroughly chilled team finally moved indoors and resorted to playing in a domed arena with plastic-lined walls, a carpeted floor and Bedlam-style acoustics. Surely, they said, it wouldn't be long before such a structure was serving its ultimate intended function as a grain silo and the Senators were back here where they belonged, under God's own natural dome.

There was a twinge of doubt among believers when the Senators won the pennant this week; they have not, after all, been a team accustomed to winning. But in fact the "Minnesota Twins," as some insist on calling them, had the worst won-lost record of any pennant winner in American League history, and in regular-season play, they were only the league's fifth best. Senators' fans were reassured; fifth is their kind of place.

So as Series fever sweeps at least part of the local populace, do your bit to encourage it. When you see a cheerful soul standing on a corner wearing an "I Like Ike" button and waiting patiently for the trolley to Griffith Stadium, don't stare. Rather, roll down the window, wave your arms and shout out in encouragement, "How about them Nats?"