The strife-torn Caribbean and Central America will be watching the levers of U.S. voting machines as if they could open the trap door of a gallows.

In this area so long accustomed to the full weight of U.S. influence -- from the Monroe Doctrine to the fall of Anastasio Somoza in Nicaragua -- U.S. elections always have been followed closely.

But the Caribbean basin is now the focus of such turmoil and terror, such intense hopes and fears, that the impact of Tuesday's vote could send shock waves through-out the area.

The conservative elites that have run several of these countries for generations, often with the aid of a ruthless military establishment, have seen the support that they traditionally drew from the United States in the name of anticommunism suddenly jerked away by the Carter administration because of the president's human-rights policy.

Their hatred and fear of the president is apparent everywhere. Carter is seen as having turned Nicaragua over to the revolutionary Sandinistas. Although his ultimate abandonment of the Somoza dictatorship was regarded as virtually inevitable, many conservatives feel Carter somehow might have averted a final Sandinista victory.

Nowhere are passions about the U.S. presidency more intense than in Guatemala and El Salvador, both of which now see themselves threatened by full-scale revolution.

"If Carter is reelected we're dead," one Guatemalan coffee grower said recently. Romeo Lucas Garcia, Guatemala's president, has denounced Carter publicly and accused him, essentially, of selling Central America out to the Cubans and Soviets.

Right-wing extremists in El Salvador, fighting both against leftists and the Carter administration's efforts to bolster a moderate reformist government there, laid siege to the residence of the U.S. ambassador last spring and marched in front of his door carrying signs reading "Carter is a communmist" and "Reagan for president."

Many observers expect the guerrillas in El Salvador to mount a major offensive beginning in mid-November. But if Reagan wins the extreme right wing both inside and outside the Salvadoran government may decide to move first.

The most radical of the area's Marxist revolutionaires claim to see little difference between the U.S. presidential candidates, but the more pragmatic leftists, such as the Sandinistas in Nicaragua, publicly expressed contempt for Reagan.

Cuban President Fidel Castro repeatedly has denounced Reagan as a danger to world peace, noting his opposition to the Panama Canal treaties and his threats to blockade Cuba in retaliation for the Soviet invasion of Afghanistan.

But Castro, who earlier had seemed no friend of the Carter administration, has recently gone even further than denouncing Reagan. He has, in the opinion of many observers, moved to bolster Carter's position in the race by shutting down the port of Mariel, from which more than 120,000 Cuban refugees inundated American shores earlier in the year and releasing 30 U.S. prisoners from Cuban jails.

Mexico, which rests secure on its vast reserves of oil in its dealing with whoever wins is probably the most complacent of the area's nations with regard to the election. But many officials have said privately that they are appalled by Reagan's initially expressed interest in something like a regional common market. "The United States may talk about interdependence," said one official, "but all such an arrangement would mean for us is total dependence, and that is what we are trying to escape."