PRESIDENT Reagan, Democrats, and critics in his own party are again attempting an uneasy ''bipartisanship'' over Central America. Uniting them is a widespread conviction in Washington that the region is deserving of United States attention, for security, political, and cultural reasons. Also uniting them is Washington's awareness that most Americans do not see Central America as a compelling issue. Only some 7 percent regard it as significant to their decision on a national officeholder - way down the list from economic issues like inflation, international tensions like the arms race, and character qualities such as leadership.
Notably, President Reagan in his major speech on the region Wednesday night refrained from partisan attacks on Congress, such has have regrettably embittered the debate over Lebanon. He gave in effect a primer of his views on the region: US national security is threatened. Soviet subversion through Cuban and Nicaraguan surrogates is intent on destabilizing the region. Hundreds of thousands of Hispanic refugees could surge across the Rio Grande. El Salvador's apparent election of a moderate president and the contra ''freedom fighters'' in Nicaragua, bearing flags of democracy, need US support.
His one attack, on ''new isolationists'' in the United States, was more a reference to his presidential opponents than an attack on his congressional critics.
Again, for good reason. He needs congressional votes. He cannot call on the American public, as he could early in his administration in his budget battles, to pressure foot-dragging Democrats and wayward Republicans.
His opposition has its own primer on Central America. It includes much of what the President did not mention: More development aid should replace the administration's emphasis on military assistance. Human rights should be affirmed, ''death squad'' activity condemned and prosecuted. The mining of Nicaraguan waters has discredited CIA involvement; further changes in covert policy should be clearly explained to relevant congressional committee members. Military aid cannot likely ''buy'' a political victory in El Salvador.
Discomfort with the bipartisan case for Central America can be read in the reactions of congressmen like Sen. Lloyd Bentsen. Bentsen, a Texas conservative, agrees with the President on aid, on the danger of a Marxist destabilization of the region, and a domino-like collapse that could send a surge of Latinos northward. Yet he says: ''My worry is that the administration at some point will go for a totally military solution.''
At some point, US pressure in El Salvador and Nicaragua must be converted into negotiation, Bentsen and many others, Republican and Democrat alike, agree.
At the moment, the President is going to the public, as he should, to gain more leash for his Central America initiatives - and a wary Congress correctly is letting out the spending leash inch by inch.