The frenetic week-long scramble for the seat being vacated by Rep. Robert Drinan (D-Mass.), the Jesuit ordered by the Vatican to give up his House seat, halted briefly today in a rare outpouring of political good-will.

The two leading contenders on the Democratic left announced that only one will run, with the support of the other -- a move urged strongly by Drinan's still tight-knit campaign committee, which will soon endorse one of the 12 Democrats suddenly thrust into this congressional race.

John Kerry, former president of Vietnam Veterans Against the War and later an unsuccessful candidate for Congress, said today he was withdrawing in favor of state Rep. Barney Frank, one of the Massachusetts Legislature's most powerful and articulate liberals.

"The race promised a useless divisiveness among friends that threatened the legacy of Bob Drinan's 10 years," said Kerry, who is searching for another race. "If Barney and I went at it tooth and nail . . . it would greatly diminish our ability to get votes in the general election."

The surprise Sunday announcement by Drinan sent newfound candidates scurrying around the district for signatures to meet a Tuesday filing deadline for nominating petitions.

"John and I kept running into each other everywhere we went," said Frank, who teaches a course on Congress at Harvard's Kennedy Institute of politics. "We kept tugging each other all over the lot."

Now, says Frank: "From the standpoint of unity, the battle has been won."

Likely to dispute that notion are several prominent state representatives and mayors on the Democratic side and three Republicans led by Newton Mayor Theodore Mann, also a liberal.