It was the best of weeks, it was the worst of weeks for Bernie Sanders.He picked up his eighth victory out of the last nine contests and outpaced Hillary Clinton in fundraising.Overshadowing those achievements was a succession of blunders and self-inflicted wounds. No one did more damage to Bernie Sanders’ presidential ambitions than the junior senator from Vermont.The wonkish Socialist-Independent-Democrat was surprisingly unprepared to delve into the details on topics ranging from his own trademark economic issues to foreign policy, especially Israel. It was painfully clear he hadn’t been doing his homework.Sanders’ exchanges with Clinton over who was qualified to be president can be traced to his misreading of a Washington Post headline. She repeatedly and intentionally sidestepped a question asked on MSNBC whether she considered Sanders qualified to be president, but the Post headline said “Clinton questions whether Sanders is qualified to be president.” The Post Fact Checker confirmed “she never said” he wasn’t qualified.But Sanders, without bothering to check the facts, had leaped in and declared the former secretary of state “unqualified.” Hillary tried to dial back the exchange but Bernie raised the heat, saying she may have the experience for the job but not the “judgment.”His biggest stumble of the hapless week was an interview with the editorial board of the New York Daily News, which published a full transcript. He fumbled questions about how he would carry out his central campaign goals like breaking up the big banks and prosecuting Wall Street executives, admitting he hadn’t studied the details or the legal implications of those moves.A Washington Post editorial found it “astonishing” that Sanders was so unfamiliar with the policy details and implications of his core issues, particularly the big banks and foreign trade. It was termed “disastrous” because it showed Sanders was “surprisingly out of his depth.”As the first Jewish presidential candidate to win any primaries, he’s been a source of pride to American Jews. He is admittedly “uncomfortable” talking about himself but when asked declares, “I am proud to be Jewish.” He has said his Jewish background and learning as a child that most of his father’s family had perished in the Holocaust helped him understand racial injustice.A supporter of Israel all his life, not just since he got into politics, he has lived there and has family there.He didn’t speak to the AIPAC convention by remote hook-up last month, as he requested, because the organization would not extend to him the same courtesy it had to Republican candidates four years ago.Unlike the Likud-leaning AIPAC, Sanders has called for a more “balanced” US Middle East policy.“Of course we are going to support Israel,” he told CNN’s Jake Tapper on Sunday, but “you cannot ignore the needs of the Palestinian people.”He called Israel’s response in the 2014 Gaza War “disproportionate” accusing Israel of killing 10,000 Palestinian civilians. When he was told the total number killed in Gaza was about 2,100, and a third to half of those were Hamas fighters, he said the number wasn’t relevant, just the need for a more balanced policy.Again, it was one more issue on which he hadn’t done his homework before making any charges.When quizzed by Daily News editors about his policy toward Israel, he was unprepared.“If I had some paper in front of me,” he said, he could answer their questions. Asked about Islamic State he admitted, “Actually I haven’t thought about it a whole lot.”Criticism from the Israeli and Jewish Right was fast and furious. A hysterical Michael Oren, former ambassador to Washington and now a Knesset member, wildly accused Sanders of a “blood libel.”His loudest Jewish critics are unlikely to vote for him in the first place, but he does reflect the thinking of many young, progressive Americans, judging by the overwhelming support they’ve given him this year. He spoke about Israel deserving security and Palestinians deserving “self-determination, civil rights and economic well being.”That may be heresy at AIPAC and in the GOP, but not for growing numbers on the Left, particularly in the Jewish community, who are unhappy with the present government’s obstructionist policies that put building settlements over building peace.The great problem, as this column has noted, is those disillusioned with Israel are drifting away.Gilbert Kahn, a professor of political science at Kean University, said Sanders “seems truly bored” by foreign policy and “not interested in the nitty gritty of these issues.”What worries Democrats most about Sanders is what happens in the highly likely event he doesn’t get the nomination.Sanders “has to decide whether he plays the Ralph Nader/2000 role and sabotages” Clinton, said veteran Washington analyst Chris Nelson.Consumer advocate and Green Party candidate Ralph Nader ran a grudge campaign against Democrats in Florida. He knew he couldn’t win but that he could take enough votes away from Al Gore in Florida to hand the election to George W. Bush.Something similar happened in 1968.Sen. Eugene McCarthy, the anti-war candidate, lost the Democratic nomination to his friend, mentor and fellow Minnesotan Hubert H. Humphrey. Instead of throwing his support behind the party’s nominee, he discouraged his followers, many of them young, from voting that year. Playing the embittered spoiler, he helped elect Richard Nixon.Sanders, like Nader and McCarthy, is a leftist icon who has energized many young and new voters. But Democrats are hoping that is where the similarity ends.Sanders has said electing a Republican “would be a disaster for this country, and I will do everything I can to prevent that.”But that won’t mean anything unless he tells his ardent followers that if he is not the candidate they must work just as hard to elect Clinton.If they stay home they will be robbing Bernie of whatever influence he might have had in the next Congress or the next administration, and they will be electing Donald Trump or Ted Cruz.