Washington — Ferment in Washington over President Carter's political future gets more deeply stirred in the final days before the Democratic National Convention. Senate majority leader Robert Byrd of West Virginia, one of the nation's most powerful Democrat, broke his long neutrality in the nomination power struggle by coming out for an open convention.
Mr. Byrd, while saying he could support either Mr. Carter or his chief rival, Sen. Edward M. Kennedy, made a breach in the hitherto secure Southern and border state defense for keeping Carter at the top of the ticket.
And Secretary of State Edmund S. Muskie, another party elder, was shown in a Newsweek poll released Aug. 2 doing slightly better than Carter against Republican nominee Ronald Reagan. While Mr. Muskie has publicly affirmed his commitment to Carter, he has not ruled out the possibility of a "higher call" from his party in the form of a draft.
The South has been Carter's base of power in seeking the White House. Among Democrats in the House of Representatives, three- fourths from the West, Midwest , and East support an open convention, according to surveys. In contrast, only one is six from the South seems willing to abandon Carter on the issue.
One of the strongest arguments -- not yet openly pressed in the convention debate -- for not dumping Carter is that Souther Democrats would be outraged at what they might take as another Yankee maneuver to humiliate the South and guarantee Mr. Reagan's election.
The Presidenths pollster, Patrick Caddell, had said last year that a Carter-Kennedy tilt threatened a divisive, bitter Democratic civil war. That theme had been played down, however, as Carter's nomination appeared assured by his primary successes.
While West Virginia is itself a border state, some argue Mr. Byrd's position could represent an entering wedge in the Southern line against an open convention. It is hoped in some circles that a Southern or border state alternative to Carter -- possibly Mr. Byrd himself -- could be found for the 1980 ticket.
Many of those supporting an open convention -- which would require a florr vote releasing delegates from state primary and caucus ties on the first ballot -- contend Carter has enough votes for renomination regardless of the rules vote outcome. They argue, as does Byrd, that Carter would be helped by a fresh, uncoerced affirmation of support from the convention itself.
However, while Carter supporters appear confident they could beat Senator Kennedy in a two-man contest on a first ballot whether or not the binding rule is dropped, they worry that a widening of entries -- including Byrd, Muskie, or Sen. Henry Jackson of Washington -- could splinter the convention. Carter's strength could quickly wane through multiple ballots, they fear.
For these reasons, an all-out Carter comeback effort to squelch the unbinding of delegates is anticipated.
Tonight's scheduled press conference, ostensibly to answer questions on a White House reply to the Senate panel inquiring into his brother Billy's Libyan ties, is being called a crucial test of the President's style by political observers here. As in the past when in trouble, Carter is expected to maintain a cool, confident demeanor in discussing his re-election prospects and at the same time attack the fairness of his opponents' tactics. He is expected to show himself as tough, in command, yet the victim of partisan maneuvering and deserving of sympathy.
Actually, Carter's comeback task is at least threefold.He must stem the open convention tide, still the "Billygate" tremors that could embroil his attention during the race, and pump enthusiasm into his public standing as a leader.
The latter task is the most fundamental, experts say.
The latest Gallup poll confirms the plunge in Carter's popularity or approval rating registered in other surveys. Only one voter in four rates him a strong leader -- down from one in three in June.
"The public's overall feeling is of stagnation, of nothing getting done," says George Shriver, managing editor of the Gallup poll. "The economic situation has to be hurting him."
But Mr. Shriver adds, "The 'Billigate' affairs is not enough to bomb him out."
Given his multiple problems, Carters is expected to fight back on several fronts at once, and vigorously. He already has labeled the open convention maneuver "a travesty" and has begun exhorting his congressional and delegate backers. He is likely to attempt to absorb the Kennedy jobs-creation thrust, both Democratic and Republican strategists agree, but not Kennedy's specific programs.