By redeploying the US marines in Lebanon, President Reagan is shedding a potential political albatross in the November election. There is broad public relief that American troops will soon be out of a no-win conflict.
At the same time the action points to the weakness of US diplomacy in the Middle East and could pose problems for the President's image as an effective helmsman of foreign policy, political and diplomatic experts say.
The question now is whether Mr. Reagan can fashion a coherent new policy that realistically takes account of the changing balance of power in the Mideast, enables the US to enhance its credibility as an objective broker, and thus mitigates the ostensible black mark a forced withdrawal from Beirut gives the Reagan presidency.
Across the political spectrum there is widespread support for Reagan's decision to withdraw the American troops from Beirut. Democrats and Republicans alike have been calling for such a withdrawal. Polls have shown Americans increasingly concerned about the US military involvement in Lebanon.
Most observers say that it is to the President's credit that he grasped the realities of the situation in Beirut and prudently decided to order the troops offshore. ''Reagan realized this is a hopeless situation, and, unlike (Presidents) Johnson and Nixon in Vietnam, he is getting out - even though he is acting against his own ideological instincts,'' one political expert comments.
Reagan campaign advisers say the redeployment helps the President politically. But they acknowledge that, depending on what happens in Lebanon and the Mideast generally, the issue may not go away by election time. ''It looks good in the short term,'' says a key GOP adviser, ''but there are too many imponderables at this point.''
''I don't know that this is as big an event politically as people think it is ,'' says a longtime Republican strategist. ''I doubt people would dump the President simply because of the marines in Lebanon. This will give the Democrats a short-term benefit. What counts is the larger question of what this means regarding our position in the Middle East.''
''Policywise, this is a minus for the President,'' says a foreign policy adviser to Walter F. Mondale. ''The marines are leaving without their mission accomplished. But Lebanon is only a sideshow for the United States - not a Vietnam. Reagan will still be able to portray himself as a tough guy, and Mondale is not going to beat Reagan by saying he will be tougher. So he'll say Reagan is engaging in 'adventurism.' But I doubt substantial fallout from the Lebanon issue.''
One imponderable is whether the President will escalate the use of air attacks and naval bombardment in order to try to prop up the Gemayal government, and what the results of such a policy would be diplomatically. Mr. Reagan said Tuesday night he had authorized the Navy to provide naval gunfire and air support against any unit firing into greater Beirut from parts of Lebanon controlled by Syria as well as against any units attacking US or other foreign pesonnel and facilities.
Most analysts here believe that such an escalation of military force would not be effective and, in fact, would worsen the situation. It is speculated that the presidential order was designed largely for political purposes - as a face-saving way to cover a military retreat. In any case, the disengagement highlights the problems for US policy in the region over the past 18 months, experts say. The effort to create a stable, pro-American Lebanon has fallen apart.
Diplomatic experts on the Middle East voice concern about what they see as the confusing signals and excessive statements of the administration. Only two days before ordering a redeployment of the troops, the President said in an interview with the Wall Street Journal: ''If we get out, that means the end of Lebanon. And if we get out, it also means the end of any ability on our part to bring about an overall peace in the Middle East.''
Reaganites say that events in Lebanon overtook the presidential comments in the Wall Street Journal. ''The circumstances changed, and so the President acted ,'' says one campaign operative. ''This demontrated the leadership that it takes to do what the circumstances require. But it doesn't mean our policy is floundering or confused. Others have an input in foreign policy over which we have no control. But Reagan is doing what he thinks is in the best interests of peace.''
Congressional correspondent Julia Malone reports:
Amid the collective sigh of relief on Capitol Hill that the marines will move off the ground in Lebanon, lawmakers still point to possible dangers and lingering controversies. And some continue to call for complete withdrawal of American troops from the shores of Beirut.
Senate majority leader Howard H. Baker Jr. (R) of Tennessee conceded on Wednesday that ''phased withdrawal'' means those troops remaining would be at risk. However, he maintained that the plan was ''the least we could do'' as support for the Lebanese government.
He also could not guarantee that Congress would approve funds to fulfill the President's offer of antiterrorist training and other support to Lebanon.
While Democrats are branding the President's policy in Lebanon as a total wash out, Republican leaders are reserving, at least for the record, some hopes for the embattled Lebanon government.
''The presence of our fleet should remind all parties over there - and over here - that the American interest in a free and independent Lebanon is going to continue,'' said House GOP leader Robert H. Michel of Illnois in a statement.
But not everyone on the Hill agrees. ''I think it's a major embarrassment for the United States foreign policy,'' said Rep. Jim Leach (R) of Iowa in an interview. Representative Leach, a member of the House Foreign Affairs Committee , opposes keeping troops in Lebanon.