When the first President Bush had disagreements with Israel over its settlement policy, he threatened to withhold loan guarantees from Israel. Mr. Obama has had his own disagreements with Mr. Netanyahu over the settlers but has never taken such a step. To the contrary, he has increased aid to Israel and given it access to the most advanced military equipment, including the latest fighter aircraft.

Ask any senior Israeli official involved in national security, and he will tell you that the strategic relationship between the United States and Israel has never been stronger than under President Obama. “I can hardly remember a better period of American support and backing, and Israeli cooperation and similar strategic understanding of events around us,” the defense minister, Ehud Barak, said last year, “than what we have right now.”

That cooperation has included close coordination by intelligence agencies — including the deployment of cyberweapons, as recent news reports have revealed — to thwart Iran’s nuclear ambitions.

Mr. Romney conveniently neglects to mention that Mr. Obama’s predecessor, George W. Bush, diverted American attention from Iran — the greatest threat to Israel’s existence — to Iraq, even helping to put a pro-Iranian leader in power in Baghdad. In contrast, through painstaking diplomacy, Mr. Obama persuaded Russia and China to support harsh sanctions on Iran, including an arms embargo and the cancellation of a Russian sale of advanced antiaircraft missiles that would have severely complicated any military strike against Iran’s nuclear facilities. Mr. Obama secured European support for what even Iran’s president, Mahmoud Ahmadinejad, called “the most severe and strictest sanctions ever imposed on a country.”

Mr. Romney has never explained how he would prevent Iran from acquiring nuclear weapons; Mr. Obama not only has declared that all options are on the table, but he has also taken the option of merely “containing” a nuclear-armed Iran off the table. He has directed the military to prepare options for confronting Iran and has positioned forces in the Persian Gulf to demonstrate his resolve.