By Fareed Zakaria, CNN

There's not much foreign policy talk on the campaign trail except for one issue - Iran. Everyone is talking about Iran's new strength and assertiveness - its missile tests, its progress on the nuclear program, its moves in Iraq. Mitt Romney, the Republican front-runner, describes Iran as "the greatest threat that the world faces over the next decade." Newt Gingrich has compared the Iranian challenge to the rise of Hitler’s Germany. More measured commentators also see Iran’s rising influence and power across the Middle East.

In fact, the real story on the ground is that Iran is weak and getting weaker. Sanctions have pushed the economy into a nose-dive. The political system is fractured and fragmenting. Abroad, its closest ally and the regime of which it is almost the sole supporter - Syria - is itself crumbling. The Persian Gulf monarchies have banded together against Iran and shored up their relations with Washington. Last week, Saudi Arabia closed its largest-ever purchase of U.S. weaponry.

The simplest measure of Iran’s strength is its currency. When Barack Obama became president, you could buy 9,700 rials with one dollar. Since then, the dollar has appreciated 60 percent against the rial, meaning you can buy 15,600 rials.

Iranian President Mahmoud Ahmadinejad told parliament recently that the latest sanctions were “the most extensive . . . sanctions ever” and that “this is the heaviest economic onslaught on a nation in history . . . every day, all our banking and trade activities and our agreements are being monitored and blocked.” The price of food staples has soared 40 percent the past few months, Reuters reported this week.

The Iranian government's reaction to the prospects of sanctions that could hit its oil exports shows its desperation. First, one of its admirals threatened to block the Strait of Hormuz, invoking the Persian expression that this would be as easy as "drinking a glass of water." But a senior commander of the Revolutionary Guards - Iran's crucial power source - quickly backtracked, explaining that Tehran has no intention of blocking the strait.

Frankly it would be madness to do so because Iran would suffer more than any country. Blocking the strait would result in a near total shutdown of Iran's exports and imports; and with 60 percent of Iran's economy coming from oil exports, that would bring the government to a standstill.

Meanwhile, Iran’s nuclear program is making progress. This is inevitable: Nuclear technology is 70 years old; Iran has a serious scientific community, and it sees a nuclear program as an emblem of national security and pride. But do we think of North Korea as strong and on the rise because it has a few crude nuclear devices?

The Obama administration has put tremendous pressure on Iran on a variety of fronts — far more pressure than the Bush administration was ever able to muster. This is, in part, because the pressure has been brought to bear, wherever possible, with other countries. The United States does not buy oil from Iran. But European nations, Japan and South Korea do, and if they go along with a new round of sanctions, Iran faces the real prospect of an economic freefall.

The Obama administration seems to have concluded that the Iranian regime is not ready or able to make a strategic reconciliation with the West. The regime is too divided and Ayatollah Ali Khamenei, the ultimate authority, the Supreme Leader, is too ideologically rigid. So for now Washington wants to build pressure on Iran in the hopes that this will force the regime into serious negotiations at some point.

This strategy is understandable. But it also risks building up pressures that could take a course of their own — with explosive consequences. The price of oil is rising during a global slump only because of these political risks. Without a carefully considered strategy, these risks will grow. Weak countries whose regimes face pressure can sometimes cause more problems than strong nations.

Read more of my thoughts on Iran in my recent column in The Washington Post. For more of my thoughts throughout the week, I invite you to follow me on Facebook and Twitter and to visit the Global Public Square every day.