When he was seven, Ed Miliband was taken to visit his grandmother in Tel Aviv. Pointing to a black-and-white photograph in her home, young Ed demanded to know who ‘that man in the picture’ was. He was told the man, David, was his grandfather and had died in Poland many years before he was born. Only years later did Miliband realise that his grandfather had been murdered by the Nazis for being Jewish.

Miliband’s parents only narrowly escaped a similar fate: fleeing Belgium as the German armies overran it in 1940, his 16-year-old father caught the last boat from Ostend to Britain. In Poland, his mother — together with her sister and mother — was sheltered throughout the war, initially by nuns: Marion Kozak would make it to Britain seven years after her future husband.

In less than a month’s time, this son of Holocaust refugees could become the first Jewish occupant of Downing Street since Benjamin Disraeli. Whatever your politics, it is a remarkable and affecting story. But it is a tale with a twist: Miliband’s relationship with Britain’s Jewish community is an uneasy one — and in this closely fought election the mutual distrust which now defines it may contribute to depriving him of the premiership.

This was made clear last month at a dinner for the Community Safety Trust, a charity which provides security for Jewish venues. When a fundraising video was screened featuring Miliband, his image was greeted with loud and widely joined-in booing. It was, says Stephen Pollard, editor of the Jewish Chronicle, ‘an astonishing moment’.

For much of the Jewish community, Miliband was a blank sheet when he was elected Labour leader. This is not altogether surprising. His parents, wrote Miliband in 2012, ‘defined themselves not by their Jewishness but by their politics’ and they brought up their boys outside the community.

On winning the leadership, Miliband appeared to embark on something of a journey. He was, says one former Labour party staffer, ‘forced to get to know the community’. At times, he seemed to enjoy the experience of finding his Jewish self. Dinners, receptions and well-received speeches to Labour Friends of Israel’s annual lunch followed. The journey culminated, last spring, in what appeared a highly personal choice for his first major overseas trip: a visit to Israel.

Miliband returned home to declare himself a ‘friend of Israel’, committed to ensuring ‘Israel’s security and right to protect itself’. That commitment would, however, be put to the test within weeks, as — following the murder of three Israeli teenagers and a wave of rocket attacks on Israel from Hamas–controlled Gaza — Israel launched Operation Protective Edge. Miliband responded by condemning Israel’s actions and suggesting that David Cameron’s ‘silence on the killing of hundreds of innocent Palestinian civilians’ was ‘inexplicable’. It was not so much Miliband’s condemnation that angered many British Jews, but its fiery nature, its lack of nuance — the apparent lack of context or empathy for Israeli civilians who found themselves under sustained attack from Islamist terrorists — and the suspicion that he was using the issue as a political football.

But for many, what was to follow was worse: the Labour leadership’s four-month silence as anti-Semitic attacks doubled at home. ‘Only when things got really bad did they feel they had to say something,’ says one community activist. ‘It felt like it took a very long time.’ This was the hardest thing for British Jews to bear, and it made many of them confused and angry.

Instead of attempting to heal the rift, however, Miliband went on to widen it, whipping his MPs last October in support of a motion backing unilateral recognition of a Palestinian state — proposed by a Labour backbencher who the month before had compared the Israeli army to Isis.

But why? What could his motive be? Some think that Miliband wishes to erase all traces of New Labour, others that he’s simply weak and has let Diane Abbott and the hard left to dictate his foreign policy. Then there are those who believe him to be a cynic, keen to keep in step with the rise of anti-Zionist, anti-Israel sentiment: these cite his so-called ‘35 per cent’ core-vote strategy. Many British Jews, however, have come to believe that this is simply where Ed instinctively is. For this last group, Miliband is part of the left for which the Palestinian struggle is of central importance.

Jews don’t form a homogeneous voting bloc, but they have in the past been a barometer: long left-leaning, they strongly backed Margaret Thatcher in the 1980s before swinging heavily to New Labour in 1997.

This week, a poll for the Jewish -Chronicle found that 69 per cent of Jews intend to vote Tory next month, with Labour trailing on only 22 per cent. Moreover, while 64 per cent said David Cameron had the best attitude towards British Jewry, only 13 per cent picked Miliband as the best supporter of the community. The Jewish Chronicle poll found 73 per cent of Jews said the parties’ approach toward Israel and the Middle East was ‘very’ or ‘quite’ important in determining how they would vote, and by 65 to 10 per cent Cameron led Miliband on having the best attitude.

Community activists believe Miliband’s position on Israel has become such a sticking point that many Jews who traditionally vote Labour can’t bring themselves to do so. One said: ‘They have been forced to choose between their party and their support for Israel in a way they never thought they would be.’ Some have already made that choice: last autumn, Maureen Lipman declared that, for the first time in five decades, she wouldn’t be voting Labour. At the same time, Kate Bearman, a former director of Labour Friends of Israel, resigned her party membership.

Even some Jewish Labour activists believe the party has written the community off electorally. This could turn out to be a costly miscalculation. There are a string of marginals — Finchley and Golders Green, Hendon, Brent Central, Ilford North, Hornsey and Wood Green, Hampstead and Kilburn, Harrow East, Harrow West and Hove — where Miliband has little room for error and Jewish voters could provide the difference between victory and defeat.

The Labour leader has, says one sympathetic observer, shown a great deal of ‘carelessness’ in his dealings with the Jewish community. If that carelessness costs him the keys to No. 10, he continues, the ‘tragedy will be complete’.