Joe Biden's decision to halt supply of arms to Israel if Rafah is invaded could come back to haunt him

All decisions have intended consequences and unintended consequences.

The intended consequence of President Biden's threat to stop sending some weapons to Israel is straightforward: to stop the Israeli military from going into Rafah without a clear, deliverable plan for the civilian population.

But there are so many unintended consequences. In Tel Aviv and on Capitol Hill they are beginning to play out already.

Both geopolitically and domestically for Mr Biden this decision could come to haunt him.

Even before we consider the unintended consequence, there is a key point: the perils of setting red lines.

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Too often they turn out to be flawed tools of geo-political diplomacy.

What if Israeli Prime Minister Benjamin Netanyahu bulldozes through the red line and invades Rafah?

He's already said he will plough on with the Rafah operation. Posturing? Maybe, but the last seven months have shown us he does what he says he will do.

Israel probably has enough American weapons in storage to roll into Rafah.

So, will Mr Biden stick to his threat to pull weapons delivery? Or will he relent? What message will both of those choices send, far and wide?

That brings us on to the unintended consequences. First, the regional consequences.

  • Greater numbers of civilian casualties: If Mr Netanyahu continues with his Rafah operation but with a dwindling supply of American weapons (so-called smart bombs) then he will increasingly use less sophisticated 'dumb bombs'. This could cause even more civilian casualties.

  • Impact on ceasefire: It's logical that Hamas may see this decision as weakening Israel and may therefore hold out in the ongoing negotiations to get more out of them.

  • Reducing leverage elsewhere: The US is consistently pressuring Israel on other issues, like opening borders to Gaza for humanitarian aid, tackling settler violence in the West Bank, resisting the urge to launch a full-scale war with Hezbollah in Lebanon. How will all that be impacted by this schism in relations?

  • An emboldened Iran? Limiting weapons to its oldest middle eastern ally at a time of profound danger for Israel is being seen by some as a gift for Tehran.

  • The message it sends: That America could be seen to abandon Israel (despite that not being what Mr Biden has said) will not be lost on countries around the world. It suggests that America is flaky with its alliances. For months, Mr Biden has dismissed calls to limit weapons supplies. Now he's u-turned. If Mr Biden blinks as Mr Netanyahu crosses the Rafah red line then the flaky image is only compounded. What does America stand for will be the question.

Then there are the domestic political consequences. And they are huge.

They were spelt out by his presidential opponent, Donald Trump: "What Biden is doing with respect to Israel is disgraceful. If any Jewish person voted for Joe Biden, they should be ashamed of themselves. He's totally abandoned Israel and nobody can believe it."

That sentiment was echoed by a band of Republican senators on Capitol Hill, incandescent with anger as they framed Mr Biden's decision as an abandonment of Israel.

President Biden has already alienated key sections of the voter population with his existing Gaza policy.

By supporting Mr Netanyahu unequivocally hitherto, he has angered key Arab-American populations in places like Michigan - a state he needs to win in November.

Beyond that, students - many of whom have been out protesting and would be natural Biden voters - say they now cannot vote for him. 'Genocide Joe' is their cry.

Now, with his weapons announcement, he risks alienating Jewish-American voters too. Many are deeply angry at what they see as an abandonment of the Jewish State.

His badly articulated insistence that he will still have Israel's back in terms of defence will be lost on many voters. They see only the headline.

Remember that pretty much all Republicans are against every lever he pulls to rein in Israel; they want nothing less than unequivocal support for Israel.

More than that though - a significant number of his own Democrats are also uneasy about America limiting weapons for Israel. Only the progressive left of his party supports his move.

It is a perilous political push-me-pull-you and the election is six months away.