Late on the evening of Sunday 17 September 1978, Anwar Sadat and Menachem Begin — watched by a beaming Jimmy Carter — signed an agreement in the East Room of the White House which brought to a close 30 years of intermittent conflict between Israel and its biggest neighbour and most dangerous enemy.

The three men had spent the previous 13 days sequestered at the presidential retreat of Camp David. Begin and Sadat refused to negotiate directly and barely spoke with one another, so the president and his team shuttled between the Egyptian and Israeli delegations, endlessly drafting and redrafting the terms of a peace agreement between the bitter foes.

While a formal agreement would not be signed for another six months — after the president had flown to Cairo and Jerusalem to seal the fraying deal — the signing of the Camp David accords 40 years ago represented the high point of Mr Carter’s tempestuous presidency and his most enduring legacy.

And yet, barely two years after that momentous day, American Jews delivered a historic snub to the president as he ran for re-election, contributing to his landslide defeat at the hands of Ronald Reagan.

Alongside African Americans, Jews are the Democratic party’s most loyal constituency; earning like Episcopalians but voting like Puerto Ricans, as the writer Milton Himmelfarb famously put it.

CAMP DAVID AT 40 IN THE JC:

• The JC's foreign editor:  Israel and Egypt today are partners — but not particularly close ones
• One negotiator remembers: "I told Menachem Begin: the pyramids were not built by the Israelites"
• Israeli experts reflect on Camp David's successes and failures

When Mr Carter narrowly won the White House in 1976, he did so with the votes of 71 per cent of them. Four years later, however, the president had the lowest share of the Jewish vote — just 45 per cent — received by a Democratic presidential candidate in the past century.

Some defected directly to Mr Reagan; a disproportionate number bolted to John Anderson, a third party candidate who attracted the support of many other disaffected liberals.

Jewish disenchantment with Mr Carter had unique causes — the so-called “kosher vote” stuck with Democrats such as George McGovern and Walter Mondale even as they went down to crushing defeats — but they nonetheless epitomise why the president was unceremoniously ejected from the White House after only one term.

These causes are laid bare in a new biography of Mr Carter by Stuart Eizenstat, who served as the president’s domestic policy adviser and also as an informal liasion with the Jewish community.

As Eizenstat amply demonstrates in President Carter: The White House Years, Camp David showed Mr Carter at his very best: his willingness to take huge political risks; his tenacity and courage; a prodigious work ethic, and mastery of the minutiae.

Moreover, the president proved himself sympathetic to Jewish concerns: pushing a law to ban US companies participating in the Arab boycott of Israel, establishing the Presidential Commission on the Holocaust under Elie Wiesel, and backing its proposal to build Washington DC’s renowned Holocaust Museum.

However, Mr Carter — who, unlike Richard Nixon, did not appear to harbour an antisemitic bone in his body — also demonstrated a startling insensitivity at times. During his first year in office, for instance, the devout Baptist managed to twice refer to the Jews’ role in Jesus’ crucifixion when preaching at Bible classes.

A generous interpretation might ascribe such gaffes to what Mr Carter’s chief of staff, Hamilton Jordan, termed the “huge cultural … gap” which existed between the president and many Jews.

The first southerner elected to the White House since the civil war, Mr Carter’s political career had been forged in rural Georgia and he lacked the familiarity and contacts with the community that many leading Democrats from states with large, urban, Jewish populations had.

But new to national politics, the president also displayed a highly unattractive combination of inexperience, arrogance and self-righteousness which decimated his Jewish support.

After running a strongly pro-Israel campaign in 1976, Mr Carter launched an ill-advised and ultimately futile effort to strike a comprehensive Middle East peace deal between Israel and all its regional enemies.

While Mr Eizenstat, Mr Jordan and Walter Mondale, his vice president, repeatedly cautioned the president of the need to assuage Israel’s legitimate security concerns — and emphasised that bringing the domestic Jewish community on board was key to the success of any initiative in the region — Mr Carter largely ignored such warnings.

The president, Secretary of State Cyrus Vance and National Security Adviser Zbigniew Brzezinski instead saw “domestic outreach as a nuisance”, Mr Eizenstat suggests.

Nor were Mr Carter’s early missteps without consequences. His unplanned public endorsement of a Palestinian homeland in early 1977 was delivered while Yitzhak Rabin was visiting America, and just weeks before Israeli Labour faced difficult elections.

His political ineptness in two botched decisions at the United Nations, just as he was fending off a primary challenge from Senator Ted Kennedy, cost him dear in 1980.

No sooner had the dust settled from the first, involving UN ambassador Andrew Young’s meeting with a PLO representative, than the administration blundered into a second: the US’ vote for an Arab-backed resolution that condemned settlements in “occupied” territory and, crucially, referenced Jerusalem.

It cost Mr Carter the New York primary and revived Kennedy’s by-then flagging campaign. The president was thus forced to endure several more weeks of party warfare, leaving him further bloodied before he faced Reagan.

Mr Carter’s belief that “the Jewish community has never given me a break” and his anger at Begin’s success at thwarting his efforts on behalf of the Palestinians after Camp David bred a lasting resentment.

Having left office at the age of only 56, he has spent nearly four decades building a strong post-presidential reputation.

Tellingly, however, he has continued to adopt a provocative stance towards Israel, symbolised by his 2006 book entitled Palestine: Peace Not Apartheid.

The book, which earned public rebukes from the Democrat speaker of the House of Representatives Nancy Pelosi and Bill Clinton, was labelled “simplistic and one-sided” by The Economist.

Perhaps, then, it is unsurprising that, having already formed a similar judgment of his handling of the Middle East, unprecedented numbers of American Jews turned their back on Mr Carter in 1980.