NOT TOO long ago, Virginia's Republicans were riding high in Richmond, with a grip on the governorship, a number of able challengers for seats in the state legislature and a philosophical if not always partisan lock on the two U.S. Senate seats. But today the Republicans are reeling from a series of devastating Democratic victories over the years that can all be traced to the exceptionally popular Charles S. Robb. And this week, Mr. Robb delivered another blow: his announcement that he will run for the U.S. Senate. It cleared not only the air but also the field. "I don't know anyone who has a realistic chance of beating him," a veteran Republican congressional aide told Post reporter Donald P. Baker, noting that no member of Virginia's delegation to Capitol Hill would risk giving up a seat to challenge Mr. Robb. Surely some Republican will rise to -- or be hauled up to -- the occasion in Virginia. Meanwhile, many Democrats inside the state and out will be watching this race with more in mind than a single Senate seat.

Mr. Robb has assumed an active role as one of the founders of the centrist Democratic Leadership Council, which he explains is part of an effort to return the national party "into the mainstream." Though his latest announcement included a disavowal of national ambition, it was hardly the stuff of a Southside clambake: "It's time once again for Virginia to lead this nation, in defining the challenges of a new political and economic era, to renew America's promise of equal and expanding opportunity, to rededicate ourselves to the defense of liberty and the advancement of human rights and social justice at home and abroad."

It sounded like a somewhat loftier route than I-95 from Richmond to Washington.