Scenario 1 - October 1973
The Watergate Story broke in October, 1972, and Senator George McGovern managed to use it to win a narrow Victory over President Richard Nixon. Exactly one year later war broke out in the Middle East with both Syria and Egypt launching a surprise attack on Israel. Soviet advisers were in open evidence on the battlefield, and the U.S. was warned not to "intervine" with military aid to the Israelis.
President McGovern was perplexed. He had done everything he could during his first nine months in office to expand Detente. The Soviets have appreciated his concession including the unilateral withdrawl from Vietnam and a cutback of U.S. Forces in Europe, but had done nothing in return. Now they were actively participating in a war against a U.S. ally.
The Israels were on the brink of using their nuclear when a counter attack just managed to save off defeat. The Soviets needed to reinforce both of their Arab allies, and launched a "limited" invasion of Turkey in order to ship heavy weapons and vehicles to the Middle East. The Turks put up a fight, and to the shock of everyone the Greeks launched an counter offensive into Bulgaria.
President McGovern tried to negotiate a cease fire but under pressure from the military order a mobilization of U.S. Forces in Europe. His planned cutback of forces of NATO forces was stalled as much as possible by the Joint Chiefs much in the way the withdrawl of Jupiter Missile bases in Europe we stalled during the Kennedy Administration. The other NATO countries began mobilization.
The Soviets had expected to take Istanbul in a few days but by the second week it was becoming clear it wasn't going to happen, and the longer they delayed an attack on West Germany the harder it was going to be. Furthermore by this time the Israels had fought Egypt and Syria to a standstill. Soviet Tank Armies crossed the border, and within the first five days had reach the outskirts of Hamburg, and threatened Munich.
General Alexander Goodpaster, U.S. Army, SACEUR (Supreme Allied Commander, Europe), used the previous two weeks to prepare for a counter attack, and using airborne and air mobile forces managed to cut off the Soviet and East Germany forces. The lack of supplies allowed U.S., West German, and French armored corps to destroy those forces, tearing a huge hole in the front lines and allowing NATO forces to invade East Germany, and threaten the Warsaw Pact's Northern flank.
For the next two weeks the fighting in Europe was confused and bloody. Heavy Soviet forces inflicted significant casualties on NATO forces, but were at a disadvantage when on the defensive. By the end of November Berlin had fallen to a combined U.S.-West German force, Czechoslovakia had declared neutrality, and NATO was closing in on the Polish border.
The Soviets demanded an end to the NATO "Invasion" and threatened to use nuclear weapons if it did not withdrawl from East Germany. President McGovern complied, and the war ended.
A statis quo had returned to Europe. Although Easter Europe remained under Soviet domination after the war, the Russian Army had been savaged during the conflict. The people living in the Warsaw Pact, and in the Soviet Union itself found themselves increasingly unsatified with their way of life.
President McGovern expected easy reelection due to the outcome of the war. His withdrawl of NATO forces on the brink of victory was seen by most as a betrayl of the people of Easter Europe and the U.S. and NATO military personel who had given their lives to preserve freedom. In the 1976 campaign McGovern was defeated by former Californian Governor Ronald Reagan in a landside.
While many feared that President Reagan would start World War Four, but his hardline against the Soviet Union eventual resulted in the collapse of that nation, and the peaceful liberation of Easter Europe by the end of his second term in 1984.
(Note: I based this on the outcome of a session of Warsaw Pact, a wargame published by Task Force Games)