THERE'S EVERY indication that Washington is ready -- in fact, long overdue -- for the return of big league baseball. In the 20 years since the Washington Senators (in their second incarnation) departed for Texas, this region has experienced tremendous growth in population and income. Even in its current economic slump, it dwarfs the Washington metropolitan area of the past in every respect. It has a good old ballpark ready to be remade at reasonable cost, a diverse population that follows teams from all over the country, a subway that goes right to the stadium and a ranking as the seventh-largest television market in the country. It is, surely, the most prominent American city without this all-American sport.

Last week the National League announced that Washington is one of six metropolitan areas that have made the final cut in the competition for two new league franchises. Three of the others are in Florida (Orlando, Miami and St. Petersburg-Tampa), which is promising new territory for baseball. The remaining two are Buffalo and Denver, both of which have proved themselves good supporters of minor-league teams. None of the finalists, however, is close to Washington in terms of television market, which is, in the game's new economic climate, becoming all-important.

Such unromantic financial considerations will probably be decisive in the allocation of the two new teams, which are to begin play in 1993. If the most important question in baseball used to be "Can he hit the curve?" it is now -- as stated in The Wall Street Journal -- "Can he write the check?" The Washington-area group of investors led by John Akridge (a group that could use one or more new financial heavy hitters) would have to be able to come up with $95 million just as an entry fee and then to field a competitive team in a game where the average player's salary is well over $600,000 and rising rapidly.

There isn't a lot the average fan can do to root home the local team of investors in the net-worth competition. But the people of this area probably will be called on soon to show their interest by subscribing to a season-ticket plan. Washington needs a good showing in that regard. Even more, though, it needs a long, fair look by the National League. The question before baseball is which cities have the depth of interest, the people and the wherewithal to support what will probably start out as a truly terrible team and then sustain it through bad times and good. If this city gets a fair appraisal, it should get a team.