On August 9, 1974, Richard Nixon's staff gathered in the White House's East Room to hear the disgraced president's farewell address. In a front-row seat, alongside members of his cabinet, sat Baruch Korff, applauding "lustily", a reporter later recalled. He was no high-ranking member of the administration, but - with the exception of Nixon's family - he had remained unswervingly loyal to the departing president for, perhaps, longer than anyone else in the room.

Three nights previously, after Nixon had decided that resignation was the only way to avoid impeachment over his role in Watergate, Korff had visited him in the Oval Office. Speaking with "the fire of an Old Testament prophet", the president later wrote, the rabbi pleaded with Nixon to reconsider. "You will be sinning against history if you allow the partisan cabal in Congress and the jackals in the media to force you from office." If Nixon was intent on this course, Korff went on, he owed it to his supporters to leave with his head held high.

Nixon did not heed Korff's advice to fight on. But, moments after he finished his East Room address, as he climbed aboard the helicopter waiting to take him from the White House to political exile in California, he turned briefly to face the cameras, flashed a broad smile and threw his arms open in his trademark "V for Victory" salute. This gesture of defiance was one which few Americans beyond Korff and Nixon's other dwindling die-hard supporters would have appreciated.

Not for nothing had Nixon introduced Korff to Chicago's mayor as "my rabbi" earlier that spring. For, during the dying months of his presidency, Korff had emerged as Nixon's most full-throated supporter. The previous autumn he had launched the National Committee for Fairness to the Presidency, which was committed to reaffirming "our faith in God and country, in constitutional government, in the presidency, and in our beloved president". Its full-page newspaper advertisements were no less effusive, charging that Nixon's media enemies had "scandalised him, brutalised him [and] savaged him day after day, night after night".

With his public appearances dogged by demonstrators, Nixon found respite in the warm reception Korff's events afforded him. At one stage in Washington, two months before his resignation, Nixon was greeted by 1,400 cheering supporters. As the end neared and members of Congress prepared to vote on impeachment, Korff stepped up his work, summoning his followers to the Capitol steps for a three-day vigil of prayer and fasting.

While many American Jews were embarrassed by his actions - the president of the Union of American Hebrew Congregations called Korff an "apologist for rampant immor-ality" - the rabbi continued to staunchly support Nixon even after his resignation and, for a period, was one of the few people to see him regularly. Korff conceded that Watergate was "wrong" but insisted Nixon had done nothing criminal.

One reporter sniffily wrote that Korff "appeared out of nowhere". Nothing could be further from the truth. Given his background, though, he was an unlikely presidential confidant. In 1919, Korff's mother was murdered in front of him during a pogrom in the Ukranian shtetl in which he was born. His father, accused of treason by the Bolsheviks, was smuggled to Poland, where Korff later joined him. In Poland, he became an ardent Zionist and, after study in yeshivas in Warsaw, Jerusalem and New York, was ordained a rabbi in 1934 - thus becoming the 73rd generation in an unbroken line of rabbis dating back to the 11th century.

Now settled in the US, Korff was the wartime director of the Emergency Committee to Save the Jewish People. Korff worked tirelessly to rescue Europe's Jews: lobbying behind the scenes in Washington; negotiating with Heinrich Himmler's henchmen to purchase Jews from the Nazis for $26 per head; and trying to persuade journalists to report the unfolding tragedy.

Korff was at the forefront of postwar efforts to persuade Britain to allow 100,000 Jewish refugees to emigrate to Palestine. He led 1,000 fellow rabbis in a march on Washington to coincide with Clement Attlee's visit, infuriating the British prime minister. Some of his tactics were less conventional: in 1947 he was arrested in London on suspicion of involvement in a Stern Gang plot to bomb Buckingham Palace. Korff was cleared but, on condition it was not revealed until after his death, the rabbi later admitted to journalists that he had been guilty. During Israel's War of Independence he was part of Menachem Begin's underground movement.

In comparison with such events, Korff's support for Nixon appears somewhat curious. Indeed, at the moment he was campaigning on his behalf, Nixon was forced to release tapes of his Oval Office conversations, some of which were littered with casual antisemitism. The president appeared obsessed with the fact that "our Jewish friends" were out to get him. He wouldn't allow, he told aides, Middle East policy to be dictated by them. The media, he agreed with Billy Graham, was controlled by them. "Washington is full of Jews," he barked when a government department reported unemployment statistics in a way he disapproved of. "Are there any non-Jews here?" the president asked when examining the lists of reporters accompanying him on his historic trip to China. His appointment of the first Jewish Secretary of State was tarnished by the revelation that Nixon called Henry Kissinger "my Jew-boy" - sometimes to his face.

But unlike many of the Jews who voted to re-elect him in 1972 - when Nixon captured the second-highest share of the traditionally Democratic Jewish vote in the past 60 years - Korff seemed prepared to give the president a pass. After his death, his daughter said her father "felt a kinship to Nixon in no small part because of his aid to Israel". That sentiment was justified. In October 1973, when Israel faced an existential threat, Nixon was consumed by Watergate. With the Soviets flying arms into Egypt and Syria, Nixon's aides debated how they could aid their ally without antagonising the Arab states who had already imposed an oil embargo. Nixon took charge and, with the command "do it now," ordered the Pentagon to start resupplying Israel's depleted forces. In two weeks, the US flew more tons of equipment and ammunition into Israel than it delivered during the Berlin airlift of 1948-9. In Tel Aviv, as the US planes arrived, traffic stopped and people began to sing "God Bless America". For that alone, Korff perhaps felt, Nixon had earned his loyalty.