Cheered on by the White House, Sen. John Culver (D-Iowa) charged into a Senate Armed Services subcommittee hearing Nov. 7 to lead a counteroffensive aimed at the biggest threat to Senate approval of a new U.S. Soviet arms-control agreement: subcommittee charman Henry M. Jackson (D-Wash.).

Culver delivered a tirade charging that leaks from the subcommittee were undermining the strategic arms limitation talks, strongly implying the leaks came from Jackson and his staff. Jackson, bending perceptibly under Culver's verbal barrage, expressed regret about the disclosures. That heightened concern by Republicans that Jackson ultimately will prove more Democrat than hawk and put party over principle.

If so, the SALT II treaty nearing agreement will win the two-thirds Senate approval needed for ratification. If Jackson oposes it, however, chances are poor. Thus, of age 65, Scoop Jackson holds the course of history in his hands.

There is no doubt about Jackson's expertise on arms control or his conviction that the new treaty dangerously widens the Soviet strategic advantage. The doubt has been whether he would treat Secretary of State Cyrus Vance as harshly as he did Henry Kissinger, risking the end of invitations to the Jacksons [WORDS ILLEGIBLE] family dinners at the White House.

Those doubts faded recently when Jackson conducted tough hearings [WORDS ILLEGIBLE] an uncomfortable, ill-prepared [WORDS ILLEGIBLE] as witness. To counteract these hearings, all 100 senators were invited top-secret briefings on SALT from the eight administraion officials on [WORDS ILLEGIBLE] 3; only seven senators showed up.

With Senate prospects fading, the [WORDS ILLEGIBLE] offensive began. The theme: [WORDS ILLEGIBLE] critics are undermining U.S. [WORDS ILLEGIBLE] negotiations. Former Deputy Defense Secretary Paul Nitze came under [WORDS ILLEGIBLE] attack for his scholarly analysis [WORDS ILLEGIBLE] adverse effect on U.S. security of SALT II agreements.

[WORDS ILLEGIBLE], tentative SALT II agreement have been leaked mainly by ad [WORDS ILLEGIBlE] officials. But this did not [WORDS ILLEGIBLE] George McGovern (D-S.D.) [WORDS ILLEGIBLE] the Senate floor Nov. 2 to Nitze of "inexcusable conduct" [WORDS ILLEGIBLE] came day, arms-control activist [WORDS ILLEGIBLE] Stone (who is secretary of the [WORD ILLEGIBLE] of American Scientists) [WORD ILLEGIBLE] letter suggesting Nitze's analy- [WORD ILLEGIBLE] subversive" and constitutes "sab- [WORD ILLEGIBLE] of SALT.

[WORD ILLEGIBLE] counter-offensive accelerated [WORD ILLEGIBLE] when our column reported [WORD ILLEGIBLE] inability to defend the SALT II [WORD ILLEGIBLE] to the Jackson subcommittee [WORD ILLEGIBLE] normally placid Vance was in [WORD ILLEGIBLE] Backing down as he never had [WORD ILLEGIBLE] Kissinger, Jackson apologized and agreed to long-standing State Department requests to inspect transcripts of Vance's testimony.

When Vance re-appeared before the Jackson subcommittee in closed session Nov. 7, Culver - a member of the full committee but not the subcommittee - made his presence felt. Finishing his third year in the Senate, Culver has become a force to contend with and the most effective instrument of the arms-control lobby. A former Harvard football player, he possesses a bulk and stentorian voice that prove intimidating to some colleagues.

Glaring down at Jackson aide Richard Perle, Culver shouted about a "hemorrhage" of secrets in our column (though they actually contain no classfied information). Jackson replied quietly that most SALT II details were being dribbled out by the administration, but Culver brushed that aside. He demanded an investigation of leaks from the Jackson subcommittee. The aim is obvious: Get Sen. John Stennis (D-Miss.), chairman of the full Armed Services Committee and a man who lives in horror of leaks, to shut down jackson.

Culver's line that leaks threaten SALT not only duplicates that of McGovern and Jeremy Stone, but also echoes what is said inside the Carter administration. Culver issued a statement to us denying his move was inspired by the administration, but that may be academic. "Thank goodness for John Culver," a senior White House aide told us. "It's about time somebody stopped Jackson from running wild."

Jackson's reaction was not reassuring to his Republican allies on the committee. Although neither he nor his staff had given us the information about Vance's appearance, he felt he must express "regret" about our column. At a joint press conference with Vance, he felt constrained to call our report "inaccurate and misleading," though he knew its accuracy had caused all the furor.

To some old hands, this recalled 1963, when Jackson first criticized the U.S.-Soviet test-ban treaty, then backed it following pressure from the Kennedy White House. But far more is at stake for U.S. security now, and Jackson is an older man with few political ambitions. How he reacts to the counterback, clearly blessed by the White House, will probably determined the fate of SALT II.