It started with an internet campaign against Robert Malley. Malley, who worked on the Clinton team at the failed Camp David Israel-Palestinian peace talks in 2000, had fetched up in a long list of people who advise Barack Obama on foreign policy.

Mr Malley, who now works for the International Crisis Group, is not on the Obama staff, or anywhere near it. But it still triggered a series of hostile comments apparently designed to undermine the candidate's credibility with Jewish voters. Most appeared in conservative blogs and websites, but according to Newsweek, attacks on Malley also surfaced in emails sent out by staffers on Hillary Clinton's campaign team.

Some of the blogs had dwelt on Malley's Egyptian-born "anti-Israel" father. But his real crime was to have challenged, including in two thoughtful articles written in 2001 and 2004 in the New York Review of Books, the conventional wisdom about the Camp David collapse. This prevailing view (one also not shared by everyone in the Israeli intelligence community) not only laid the blame exclusively on Yasser Arafat but also held that the Palestinian leader never wanted a real and lasting two state solution to the conflict.

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It was one issue Malley disagreed about with Denis Ross, his immediate boss at Camp David, in his 2004 piece, a lengthy but respectful critique of Ross's book about the peace process.

The other was that Malley took a more forward position than Ross, post Camp David, in urging that the US, "building on" the Clinton blueprint for a solution, "ought to push the parties toward ending their conflict, rather than wait until they are somehow ready to do so."

As interesting as the anti-Malley campaign, however, was the phalanx of former US Middle East diplomats who sprang to his defence against "vicious, personal," claims that he "harbours an anti-Israel agenda." They issued a statement saying that whatever "the real differences between us" the smears were "an effort to undermine the credibility of a talented public servant who has worked tirelessly over the years to promote Arab-Israeli peace and US national interests." The signatories included two experts now on the list of advisers to Hillary Clinton's campaign: Sandy Berger and Martin Indyk, Daniel Kurtzer – appointed by President Bush as US ambassador to Israel from 2001 to 2005 – and Ross himself.

Unwittingly or not, the diplomats were saying something important about the impoverished discourse on the Israel-Palestinian conflict in American politics. By defending Malley, those who knew his work best have drawn attention to a fact US aspirants to high office usually feel it is essential to ignore – Hillary Clinton's lavish praise for the West Bank separation barrier as currently routed springs to mind – namely that it is not necessarily "anti-Israel" to criticise Israeli policy from time to time.

But actually it goes deeper even than this. In the world view of many in the American Israel Public Affairs Committee, the most powerful – though not necessarily the most representative – Jewish lobbying group in the US, attitudes to the Middle East are zero sum. You are pro-Israeli or pro-Palestinian but you cannot be both. This of course conveniently buries a key argument – one heard far more in Israel than in US debate – that an urgent end to the occupation is in Israel's as well as the Palestinians' interest. In a Haaretz article this week Akiva Eldar pointed out that AIPAC "does not really bother to rally in favour of a two state solution". While those it sees as "friends of Israel" certainly include hardliners who believe in a greater Israel stretching from the Mediterranean to Jordan, those who criticise Israel for not moving fast enough in its own long-term security interests towards the just two state solution it says it wants, are enemies.

This is all the more perverse, now that the Israeli Prime Minister, Ehud Olmert, has suggested publicly that the failure to negotiate a peace with the Palestinians may imperil Israel's very existence as a Jewish state. Yet it remains hard to imagine a US politician bold enough to say the same thing without risking his own electability.

To go further still, of course, and suggest limited engagement with Hamas, as Malley has also done, is beyond the pale. Yet is it really "anti-Israel" to do so when a growing clutch of Israeli ex-generals, academics, and Israel's most celebrated novelist Amos Oz – all serious Zionists who unlike AIPAC's most hawkish members actually live there – also want talks with Hamas on one issue or another?

Is it necessarily "anti-Israel" to suggest that a Gaza ceasefire agreement with Hamas might be a better way of securing the release of Corporal Gilad Shalit and bringing peace of mind to the beleaguered citizens of Sderot – one of whom was killed yesterday by a Qassam rocket – than a perilous military invasion, when an opinion poll yesterday shows that 64 per cent of Israelis want just such an agreement?

It is a safe bet that Obama will not be urging talks with Hamas. But last Sunday at a private meeting with Jewish leaders in Ohio he did make a small contribution to unfreezing the debate on the Middle East in American politics. For the candidate identified "a strain within the pro-Israel community that says unless you adopt an unwavering pro-Likud approach to Israel that you're anti-Israel" and added: "That can't be the measure of our friendship with Israel." This may seem stunningly obvious, yet it has attracted accusations of "interference" in internal Israeli politics.

The breaking of one taboo, however modest, raises the question of whether he might, if elected to the White House, break another by seeing the conflict as a first term agenda item. For if Olmert is serious about wanting a deal with Mahmoud Abbas but is being thwarted by internal political pressure, probably the only thing that could save it is the full throttle engagement of a US administration which Malley, among others, long sought; an engagement which for all his warm words, Bush has so far all but eschewed, insisting that the US can only "facilitate" a process when both sides really want it.

The critics are divided between those who see Malley's – and Jimmy Carter's point man Zbignew Brezinsky's – appearance on the Obama list as sinister despite their minor-to-negligible role; and those like the New Republic editor Marty Peretz, who combine support for Obama with resolute defence of Israeli policy over many years, and has insisted Obama would not dream of taking Malley's advice. In fact the greater danger would not be if Obama did listen – among many others – to people like Malley, a man who has long argued persuasively that a just peace would be directly in US and Israeli interests, but if he didn't.

d.macintyre@independent.co.uk