The speech Israeli Prime Minister Benjamin Netanyahu is slated to give to a joint session of Congress Tuesday is one of the most critical of recent times. It concerns not only the very existence of his nation, but also the terribly real possibility of nuclear holocaust in the foreseeable future. Our own security is at stake as well: Iran is developing intercontinental missiles capable of carrying nuclear weapons that will reach our shores.

The question isn’t why should Congress listen to what he has to say, but rather why in the world would certain members not to hear him out?

Iran’s ability to not only attack, but also to intimidate other countries into meeting its demands would increase exponentially with its acquisition of nuclear capabilities. Imagine Tehran “suggesting” to European countries how to treat their growing Muslim populations? Sharia law, anyone?

Prime Minister Netanyahu will speak on the prospect of Iran being able to develop nuclear weapons.  He is making this speech because – like many people – he is fearful that the agreement President Obama wants to strike with Iran would not put in place effective controls to prevent the mullahs – and plausibly in turn the many terrorist organizations they actively support – from acquiring weapons-grade fissionable material.

Iran’s ability to not only attack, but also to intimidate other countries into meeting its demands would increase exponentially with its acquisition of nuclear capabilities. Imagine Tehran “suggesting” to European countries how to treat their growing Muslim populations? Sharia law, anyone?

The Obama administration has tried to discredit Prime Minister Netanyahu and dismiss his appearance on Capitol Hill as a political stunt tied to the upcoming Israeli elections.  Some of the president’s followers in Congress have vowed to boycott the speech.  But their red herring arguments cannot be allowed to disguise the crucial importance of his visit or of the issue that has prompted it.

Allowing Iran to join the nuclear club – or come perilously close -- would trigger a frightening round of weapons proliferation.  Egypt, Turkey, Saudi Arabia, and other countries in the region would all be understandably motivated to similarly arm themselves. The Middle East of today, which far too often teeters on the brink of meltdown, could in comparison seem a relatively stable, peaceful place.

And make no mistake, the specter of the revolutionary government of Iran armed with nuclear weapons does not just threaten the Middle East. Iran is believed to already possess missiles capable of delivering a warhead to Israel and perhaps even Europe.  Development of more powerful models that would extend their range to include the United States is just a matter of time. Iran’s ability to not only attack, but also to intimidate other countries into meeting its demands would increase exponentially with its acquisition of nuclear capabilities. Imagine Tehran “suggesting” to European countries how to treat their growing Muslim populations? Sharia law, anyone?

But obviously, the nation most likely to first suffer from Iran’s nuclear ambitions is Israel.  That is why it is so important for members of Congress to listen to Prime Minister Netanyahu.  The United States and Israel have a longstanding friendship that has always enjoyed strong bipartisan support.  We cannot refuse our close ally at least the opportunity to explain how a nuclear Iran would affect it.  No one demands that every member of Congress agree with the Prime Minister, but they all have a duty to listen to him.

Additionally, Congress definitely has a fundamental obligation – to the American people and the world - to be actively involved in this policy decision.  This is not Obamacare or regulating the Internet.  The consequences of allowing President Obama to go it alone with another opaque executive action could not only be catastrophic, but also impossible to remedy with after-the-fact legislation.  Once Iran has the bomb, the game is over.

The stakes here could not be higher – Israel’s continued existence, America’s moral authority, nuclear conflict, and the ghastly breakdown of world order.  Party politics cannot be allowed to interfere with bringing this matter to the most successful resolution possible.  Congress must listen to Prime Minister Netanyahu -- and so should President Obama.

Steve Forbes is Chairman and Editor-in-Chief of Forbes Media. His latest book, "Reviving America: How Repealing Obamacare, Replacing the Tax Code, and Reforming the Fed will Restore Hope and Prosperity" (McGraw-Hill Education, December 10, 2015).