By Gideon Rachman

Campaign camp-followers can find themselves staring at the dreaded underside of the bus for any number of reasons. Barack Obama, the probable Democratic party candidate, committed the most famous act of bus-related violence when he finally disowned the Rev Jeremiah Wright – his spiritual mentor. John McCain, the Republican candidate, has had to rid himself of various advisers who were too close to lobbyists.

Two recent incidents illustrate that making controversial remarks about Israel is particularly risky.

Last week, Mr McCain chucked a televangelist under the bus. Mr McCain had previously courted the Rev John Hagee, in spite of the fact that he holds a number of unorthodox views. Mr Hagee believes, for example, that the European Union is headed by the Antichrist and will unleash the war that leads to the Apocalypse. This is a serious misunderstanding of the role of the EU – but not a sackable offence.

However, when it emerged that Mr Hagee also believes that Hitler and the Holocaust were part of God’s plan to drive the Jews from Europe to Israel – a necessary precondition for the Apocalypse and the second coming – Mr McCain denounced his "deeply offensive" views. The fact that Mr Hagee is fervently pro-Israel (for his own reasons) – and that several Israeli prime ministers have embraced him as a friend – was not enough to save the rabid reverend.

Since the second coming is not a campaign issue, the Hagee story does not have many policy implications. Not so with the Obama campaign’s decision to get rid of Robert Malley, an adviser on the Middle East.

Mr Malley was part of the American team at the Middle East peace negotiations during the Clinton administration. He has argued that Israel – as well as the Palestinians – bore some responsibility for the failure of the talks.

This view made him deeply suspect among some supporters of Israel. By February the attacks on him on the internet had become so vitriolic that several senior officials in the Clinton administration – including Martin Indyk and Dennis Ross – issued a joint statement deploring the "vicious personal attacks" against Mr Malley, adding that "claims that he harbours an anti-Israel agenda" are "unfair, inappropriate and wrong".

This month, however, it was revealed that Mr Malley had met officials of Hamas, the Palestinian Islamist party that governs Gaza. Since Mr Malley works for the International Crisis Group – a think-tank – holding such meetings is part of his job description.

Such subtleties are lost, however, in a presidential election. The Obama campaign swiftly announced that Mr Malley "has no formal role in the campaign and he will not play any role in the future". Steve Clemons, a Washington pundit, remarks: "They didn’t just throw him under the bus. They reversed it back over him."

Mr Obama is alarmed by the accusations that he is anti-Israel. Last week he spoke at a synagogue in Florida, repeatedly emphasising his deep support for Israel. In a recent interview with the Atlantic magazine he said that: "My position on Hamas is indistinguishable from the position of Hillary Clinton and John McCain."

That is a shame. How to deal with Hamas is one of the central questions in the Middle East. It is legitimate to argue that Hamas is a terrorist organisation that should be shunned. But since there is no presidential candidate prepared to put the opposite view, the US will not witness a proper debate on this crucial issue.

This taboo is all the more bizarre since the Israeli government itself is currently negotiating with Hamas – through indirect talks sponsored by Egypt. A slew of senior figures in the Israeli military and intelligence establishments advocates going further and talking directly to Hamas. A senior adviser to Mr McCain remarks: "It is easier to have an open discussion on Palestine in Tel Aviv than in Washington."

Why is the American debate so constrained? The "Jewish vote" is relatively small. But Jewish voters are important in crucial swing states – such as Florida and Pennsylvania. Many Christian evangelicals – a far more numerous group than the Jews – are also fervently pro-Israel.

Finally, there is the hassle factor. Dealing with accusations of anti-Israeli sentiment is a draining and time-consuming business for a presidential campaign. It is easier just to chuck a controversial adviser under the bus – and drive on.

But American absolutism on the Middle East is reducing US influence. Last time I was in Jerusalem, Israeli officials complained to me that the US’s refusal to talk to the Syrians was foolish – since it missed an opportunity to prise apart a Syrian-Iranian axis. Now it turns out that the Israelis themselves are holding talks with Syria – but sponsored by Turkey, not the US.

Similarly, this month’s deal to restore a fragile peace in Lebanon was negotiated without the participation of the US. And it has been left to the Europeans to take the lead in nuclear negotiations with Iran.

Jon Alterman, head of the Middle East programme at the Center for Strategic and International Studies, a Washington think-tank, says: "I can’t remember a time in the last half century where the US has had so little influence in the region."

Have the main presidential candidates noticed this? Probably not. They are too busy chucking their advisers under the bus.

The Financial Times