(SIS) orchestrated what Politicos Steve Usdin described as an influence campaign "without parallel in the history of relations between allied democracies" to undermine U.S. politicians opposed to American participation in World War II—much of which was documented in a declassified history by William Stephenson, the head of the SIS front organization British Security Co-ordination (BSC). Usdin stated that "SIS ... flooded American newspapers with fake stories, leaked the results of illegal electronic surveillance and deployed October surprises against political candidates." 1960 election (by Soviet Union) Adlai Stevenson II had been the Democratic Party presidential nominee in 1952 and 1956, and the Soviets offered him propaganda support if he would run again for president in 1960, but Stevenson declined to run again. Instead, Soviet leader Nikita Khrushchev backed John F. Kennedy in that very close election, against Richard Nixon with whom Krushchev had clashed in the 1959 Kitchen Debate. On 1 July 1960 a Soviet MiG-19 shot down an American RB-47H reconnaissance aircraft in the international airspace over the Barents Sea with four of the crew being killed and two captured by the Soviets: John R. McKone and Freeman B. Olmstead. The Soviets held on to those two prisoners, in order to avoid giving Nixon (who was the incumbent Vice President of the United States) an opportunity to boast about his ability to work with the Soviets, and the two United States Air Force officers were released just days after Kennedy's inauguration, on 25 January 1961. Khrushchev later bragged that Kennedy acknowledged the Soviet help: "You're right. I admit you played a role in the election and cast your vote for me...." Former Soviet ambassador to the United States Oleg Troyanovsky confirms Kennedy's acknowledgment, but also quotes Kennedy doubting whether the Soviet support made a difference: "I don't think it affected the elections in any way." 1968 election (by South Vietnam) In the last months of the presidential election between Richard Nixon and Hubert Humphrey, President Lyndon B. Johnson announced an October surprise, intended to aid Humphrey, by declaring a cessation to the bombing in the ongoing Vietnam War and a new round of peace negotiations. In response, Humphrey's popularity grew, eventually leading Nixon by three percentage points. However, the South Vietnamese government, in consultation with the Nixon campaign, announced three days prior to the election that they would not be participating in the talks, and Nixon went on to win