Carter administration stategists estimate they can now count on about 50 of the 67 votes needed in the Senate to ratify a new Panama Canal treaty, with an intense, emotional national debate ahead to win the other 17.

The public disclosure of the basic elements of the new treaty, administration sources said last night, should swing some additional votes behind the pact in the next few days "No one, however, minimizes the battle ahead" to obtain all of ther equired two-thirds vote in the Senate, one planner said yesterday.

"Of course we think we can sell it," said another administration strategist, "but this will be a helluva fight."

Inside the Carter White House, the impending contest over the treaty is regarded as not only the first great test of the administration's abilith "to deliver" on its foreign policy, but also its most formidable public challenge.

As President Carter returned to Washington last night from a six-day stay at his home in Plains, Ga., the White House was preoccupied with down-to-the-wire negotiations on the treaty in Panama City.

A team of planners on treaty strategy, headed by chief presidential assistant Hamilton Jordan, were present to confer with Carter. Senior advisers on congressional relations from the White House and the State Department expectantly waited for decisive news from the Panama talks, and a decision by Carter, to flash word to key members of the Senate and House on the accord.

The announcement came a little after [WORD ILLEGIBLE] p.m., first after Carter reached [WORD ILLEGIBLE]

[WORD ILLEGIBLE] probably more of a domestic political issue than it is a foreign [WORD ILLEGIBLE] issued," said one planner.

Some critics would agree. In the 1976 Republican presidential election [WORD ILLEGIBLE] campaign. Ronald Reagan won loud cheers by assailing Panama Canal negotiations as a secret [WORD ILLEGIBLE] away." Reagan's battle cry [WORD ILLEGIBLE] bought it, and we paid for it, we built it and it is ours and we intend to keep it."

The Ford administration, Reagan charged, was preparing to hand over one of the itation's proudest possessions to "a Marxist, military dictator" in Panama, jeopardizing defense of the Western Hemisphere.

Similar statements have echoed through the Senate and House for years, with opponents piling up impressive, but never-controlling votes, intended to block all negotiations "to surrender" the canal or yield any U.S. control over it.

A huge lobbying campaign against a new treaty has spread across the nation, intensifying as the negotiations with Panama approach a climax.

"The other side is geared up massively," an administration official said yesterday. "They can outmail us, they can outscream us. It's easy to fan fires until you have the facts. They've had their political demagoguery, but we have the facts now - and we can sell them."

Disclosure of details of the treaty, administration officials said, will show that instead of bing "a giveaway," the pact replacing the 1903 Panama Canal treaty is "an act of statesmanship." It will preserve "the vital interests" of the United States in the waterway even after the year 2000 when Panama would acquire full control of the canal, these officials said.

In addition to the treaty itself, U.S. sources said that the agreement also will require some "implementing legislation" in the House for a new agency that would be created to operate the waterway.

As a result, the administration is planning an intensive campaign to win House support for the agreement even though the key test will come in the Senate.

The chief opponent of the treaty negotiations in the Senate, Strom Thurmond (R-S.C.), obtained as many as 39 supporters, his office said yesterday, in his 1975-76 campaign against any surrender of U.S. "sovereign rights and jurisdiction" over the canal. That signified a comfortable margin over the 34 votes needed to block a treaty, if Thurmond could hold that support.

But that strength has dissipated so much, administration officials contend, that Thurmond did not reintroduce his resolution in the current session of Congress. Thurmond forces dispute that, saying they chose, instead, to launch a lawsuit in U.S. District Court here over the Panama Canal, contending that only the congress has constitutional authority to dispose of U.S. territory. The court put off the case.

A recent poll by the Institute for Conflict and Policy Studies, a Washington based organization, said 37 of the 100 members of the Senate are inclined to favor the Panama Canal treaty being negotiated. It said 25 senators indicated opposition to a new treaty, with 33 undecided, and five listed as "no comment".

Administration sources said yesterday that their estimate of "about 50" senators already indicating support of a new treaty is based on private discussions with senators about the actual terms of a treaty.

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Public attitudes, however, administration strategists concede in private, may be more difficult to change than congressional attitudes. "It's going to be an uphill battle for public opinion," said one U.S. official.

Sen. Jesse Helms (R-N.C.), who has been a major opponent of the treaty negotiations, said yesterday that a new poll shows that Americans by a wide margin favor continued U.S. control of the Panama Canal.

United Press International said Helms made available the results of a nationwide poll of 1,011 adults conducted by the Opinion Research Corp., of Princeton, N.J. The poll reportedly showed that 78 per cent of those interviewed favored retaining U.S. control of the canal, 8 per cent favored turning over the canal to Panama, and 14 per cent expressed no opinion.

Administration officials counter that polls based on questions of U.S. "control" or ownership" of the canal miss the central points at issue and are inadequate to reflect what attitudes will be when the administration makes its case on access to the canal. These officials do not minimize the difficulty, however, of overcoming the emotions built up for 74 years over the canal as a symbol in American life.