While the Bert Lance affair gets most of today's headlines, many administration officials are more concerned about a battle that President Carter must face on another political front - the contest over the Panama Canal treaties.

They fear that White House preococupation with the Lance controversy will hinder the President in mobilizing for a fight whose outcome could have even greater effects than the fate of his embattled bufget director.

Less thantwo weeks ago, on the eve of the Sept. 7 signing of the treaties administration sources were calling the struggle for Senate approval of the pacts the issue certain to dominate the White House's list of priorities in the days just ahead.

At stake, they said, is a potentially decisive test of Carter's future ability to deliver on foreign policy agreements with other governments.as one White House official bluntly put it, "The President cannot afford to be defeated on Panama."

Within the administration, that is still regarded as an accurate assessment of the situation. But the timetable for getting the treaty-selling campaign into high gear has been thrown into disarray by the Lance affair.

Says one senator sympathetic to the treaties: "A lot of precious time is being lost. As faras i can see, the administration really hasn't done very much yet except hold a lot of meetings between people from the White House and the State Department."

That he adds, is a matter that should be causing the White House some serious concern. The dominant opinion in congressional circles is that, today opponents of the treaties are much closer to mustering the 34 senate votes needed to defest them that the administration is to getting the 67 votes it needs to put the agreements into effect.

Since more than 40 senators are counted in the undecded column, there is still ample opportunity to swing the situation around between now and the time the treaties come up for a vote, probably in january or February. But it's going io co an uphill battle.

The campaign against the treaties is being orchestrated by the Conservative Caucus, a coalition of rightist groups and politicians that has demonstrated it spotency in aiding the fights against common-site picketing and instant voter registration.

The caucus so far had been disappointed in its hopes of induring Ronald Reagan, the contiuing hero of American conservatives, to become the symbolic leader of the anti-treaty forces. But it has managed to put together one of the most intensive lobbying and public relations efforts that this country has seen outside of a presidential campaign.

Its main thrust, outside of direct lobbying on Capitol Hill, involves an attempt to put massive pressure on wavering senators through public opnion.Under the leadership of Richard Viguerie, a direct-mail expert for conservative causes, the country is being flooded with letters condemning the treaties; and key uncommitted senators such as Howard H. Baker (R-TENN.) and Lloyd Bentsen (D-Texas) are being marked as targets of ads in their home-state newspapers, urging their constituents to demand that they vote against the pacts.

The oppositions also is bidding for the support of undecided senators and voters by moving quietly away from the shrill "We bought it, we built it,and it's ours" line to more sophisticated arguments.

Increasingly, its main line of attack is focusing on the contentions that the treaties represent a retreat from U.S. global responsibilities, pose a danger to the country's military defenses and violate the Carter administration's own human-rights policy through concessions to the allegedly repressive regime of Panama's military dictator, Gen. Omar Torrijos.

Administration officials concede that they've been slow in gearing up to counter this onslaught. Although the Lance affair has been the main problem, they note that the administration has been hampered by the impossiblity of trying to sell the treaties until they were actually negotiated and signed and by the need to rework strategies originally based on an assumption that the pacts would be voted on before the scheduled congressional adjournment next month.

In addition, as one State Department officials observes, the Carter White House, with its aversion to rigid lines of authority, "is a disorganized place where things tend to be done on a free-floating, catch-as-catch-can basis."

That is evident from the difficulty one has in pinpointing who's actually in charge of the administration campaign. Although the President has promised to lead the fight personally and has designated Hamilton Jordon, his chief political adviser, as his principal strategist, they clearly are not dealing with the treaty fight on a day-to-day basis.

Below their lavel administration sources say, a variety of people are responsible for various aspects of the campaign.

In the main, Jordon seems to have delegated most responsiblity for coordinating the effort to two White House assistants, London Butler and Joseph W. Aragon. At State the department most closely involved in the canal battle, the main coordinating has been assigned to Douglas J. Bennet Jr. the assistant secretary for congressional relations.

In the weeks ahead, administration source say, the lobbying campaign is likely to become a full-time preoccupation for the Ehite House congressional relations team headed by Frank B. Moore and Bennet's State Department crew.

In addition, the administration plans to bolster the lobbying effort with a number of prominent people who have either credentials of expertise on the canal issue or special entree to the club-like atmosphere of the Senate.

Among those expected to be especially visible in this effort are the two treaty negotiators, Fllsworth Bunker and Sol M. Linowitz, both highly respected figures on Capitol Hill; former Democratic National Chairman Robert Strauss, whom one White House aide describes as "the best political operator in town," and Gale McGee, the Wyoming Democrat who was defeated last year after 17 years in the Senate and who now serves as Carter's ambassador to the Organization of American States.

Under the administration's evolving game plan, they probably won't be fully unclashed until the Senate Foreign Relations Committee completes a lengthy series of hearings on the treatics scheduled to begin in Sept. 26.

"There's lots of talk about arm-twisting by the administration," McGee adds,"but it's not really the kind of situation where you can do that. If anything, the leverage for threatening someone with political consequences is on the other side where there's a clear, highly vocal and highly emotional constituency for keeping the canal."

"Similarly," he says, "it's not a horse-trading situation where you give a guy a dam in exchange for a bridge. In the end, we're going to get votes only by making sure that senators know the facts and understand why a vote for the treaties is in the interest of the country and their constituents."

His words underscore the importance of the other prong or the administration's campaign ' influencing the Senate vote by swinging public opinion behind support of the treaties.

Although opinion polls indicate that a majority of Americans oppose the treaties, administration strategists believe that most of the negative responses come not from unyielding, hard-core opponents but from people who don't really understand what the treaties say or do to the U.S. stake in the canal.

According to this view, the bulk of public opinion on the canal issue is really unformed and susceptible to persuasion by a public education campaign.

To accomplish that goal, pians are being drawn for a broad-gauged effort that will extend from the President and the biggest names in his government down through a small army of young and anonymous foreign service officers.

The White House is now debating how Carter's leadership role can be exploited most effecctively in the weeks ahead. At a minimum, the planning calls for at least one nationally televised "fireside chat" by Carter on the subject of the treaties, the timing of which is still uncertain.

As a backup to the big names, plans are being made to enlist a little-known, but potentially important, program of the State Department in the sales pitch. That involves the department's practice of sending Foreign Service officers around the country to give lectures and briefings ofn foreign policy topics before schools, civic groups and other organizations.

Department officials are skittish about talking about the link between this program and the canal controversy since it could lead to charges that ostensibly apolitical career diplomats are being used forpartisan purposes.