It is understandable that the Republican presidential contenders should focus on the economy, which is far and away the biggest concern of voters. President Obama is sinking in the polls, hitting new lows in a series of national surveys, and so naturally everyone wants to know how he is on top of the jobs issue. But both Obama and his would-be Republican challengers have nearly entirely ignored the threat posed by Iran’s nuclear weapons program.

The Post’s editorial board observes today:

Iran has taken two more steps toward producing a nuclear weapon. According to a report released Friday by the International Atomic Energy Agency, it has begun to use a new, more advanced centrifuge to enrich uranium, which could allow it to produce bomb-grade material in a much shorter time period, should it choose to do so. It also has begun installing centrifuges in a facility dug into a mountain near the city of Qom, which could be nearly invulnerable to a U.S. or Israeli air attack. Iranian officials say those centrifuges will be used to triple the production of uranium enriched to 20 percent, creating a stockpile for which Tehran has no plausible legitimate use.

The report underlines the fact that, contrary to the impression often promoted by the Obama administration, the danger that Iran will become a nuclear power is growing, not diminishing. Administration spokesmen often speak of what they say has been the crippling effect on the Iranian economy of sanctions that have been stepped up during the past two years. Extensive media reports have told the sensational stories of computer viruses that may have disabled 1,000 or more Iranian centrifuges and assassinations that have eliminated several Iranian scientists.

Nevertheless, Congress, the administration and the Republican presidential contenders seem to be sleepwalking. How long before we hear that we have a choice between war and a nuclear-armed Iran?

Iran’s nuclear weapons capability is not merely a problem for Israel, although it is an existential threat to the Zionist premise that Jews should have a safe and secure country of their own. Iran is also a threat to the United States and to the West more generally. With Iran’s increasing missile capability, Paris, Munich and New York will all be under the threat of a revolutionary state’s apocalyptic ambitions. And should Iran obtain what two presidents have declared “unacceptable,” American credibility and leadership would be decimated.

In earlier debates Rep. Ron Paul (R-Tex.) idiotically argued that Iran should be entitled to go nuclear; Rick Santorum let him have it. But where are the leading candidates on the issue? I don’t think Texas Gov. Rick Perry has discussed it at all since announcing his candidacy. The word “Iran” was not uttered in his speech to the VFW. We don’t know what Mitt Romney (who mentioned Iran in passing in his VFW speech) or Rep. Michele Bachmann’s approach to Iran is, although both have been in the race for months.

Part of the problem is the debate moderators who relegate national security to the tail end of the questioning. But the candidates are responsible for driving the debate and explaining what their position is on the gravest threat to America’s security. By ignoring Iran they convey a certain cluelessness about national security and confusion about priorities. Why discuss Obama’s flawed Libya tactics but say nothing about the complete failure of Obama’s sanctions approach to slow the mullahs’ nuclear ambitions?

Even if not asked, any candidate who brings up the Iranian threat and sketches out his or her position tonight deserves credit. The economic crisis is real; the Iranian nuclear threat is fatal. It’s time to start talking about it.