Over the last 24 hours since the Department of Justice announced that they had foiled an alleged plot to assassinate the Saudi ambassador to the United States linked to members of Iran’s Quds Force, there has been a range of reactions from across the spectrum.
Some analysts and commentators said that the highest echelons of the government of Iran were responsible and called for immediate U.S. retaliation.
Mark Dubowitz of Foundation for Defense of Democracies asserted that the alleged plot “was likely authorized at the highest levels of the Iranian government,” and “was not a ‘rogue’ operation.”
The Wall Street Journal called in ambiguous terms for a new U.S policy on Iran:

“Iran is about much more than these antic rants, and its resources are vastly greater than al Qaeda’s. It sees itself as at war with the U.S., Europe, Israel and now obviously Saudi Arabia. As obvious, it sees itself as immune to effective retaliation against its repeated, or planned, offensives. It’s past time for U.S. policy toward Iran to reflect the reality of what it is dealing with.”

And the Heritage Foundation who unequivocally endorsed military retaliation against Iran, calling for the U.S. to “take strong measures to respond to Iran’s actions, including conducting a proportional military response against suitable, feasible, and acceptable targets (in many ways the situation is similar to military operations conducted against al Qaeda in Pakistan).”
United Against Nuclear Iran repeated its call for the U.S. to consider itself at war with Iran:

“Iran is by any definition a wartime enemy of the United States, as evidenced by their just-revealed plans to commit terrorist acts on our soil, their killing of U.S. troops in Iraq and Afghanistan, and their alliance with al-Qaeda. As such, President Obama and U.S. policymakers should treat Iran as it would any other nation at war with the country, including sanctioning the Central Bank of Iran…”

In Congress, Representative Peter King (R-NY) hinted at military action:

[W]e should not be, I don’t think, automatically saying we’re not going to have a military action. I think everything should be kept on the table when you’re talking about a potential attack against the United States, an act of war.

And Senator Mark Kirk reiterated the demand that the U.S. impose sanctions on Iran’s central bank to collapse Iran’s economy:

“What the administration should do is prepare to move against Bank Markazi [Iran’s Central Bank] in response to the bomb plot…Their currency would become like North Korea’s currency.”

But there has also been a healthy dose of skepticism about the allegations.
Christian Science Monitor ran a piece entitled, “Why Iran Assassination Plot Doesn’t Add Up to Iran Experts,” noting questions raised about the allegations from U.S.-based Iran analysts.
Reuters ran a similar piece highlighting skepticism among Middle East analysts, “U.S. Plot Charges Face Skepticism in Middle East.”
Gary Sick took to his personal website to question the allegations:

“Iran has never conducted — or apparently even attempted — an assassination or a bombing inside the US. And it is difficult to believe that they would rely on a non-Islamic criminal gang to carry out this most sensitive of all possible missions. In this instance, they allegedly relied on at least one amateur and a Mexican criminal drug gang that is known to be riddled with both Mexican and US intelligence agents.  Whatever else may be Iran’s failings, they are not noted for utter disregard of the most basic intelligence tradecraft, e.g. discussing an ultra-covert operation on an open international line between Iran and the US. Yet that is what happened here.”

Salon’s Glen Greenwald writes:

“What’s most significant is that not even 24 hours have elapsed since these allegations were unveiled. No evidence has been presented of Iran’s involvement. And yet there is no shortage of people — especially in the media — breathlessly talking about all of this as though it’s all clearly true.”

And Bob Baer, a former CIA case officer, spoke with several outlets about his own questions:

“Sloppiness about the case that defies belief…Maybe things have really fallen apart in Tehran, or maybe there’s a radical group that wants to stir up the pot…But the Quds are better than this. If they wanted to come after you, you’d be dead already.”

For its part, the Obama Administration has asserted that the U.S. would “hold Iran accountable” but has been careful not to implicate the entire Iranian government, stating instead that the alleged plot was “sponsored by elements within the Iranian government.”  Still, Secretary Clinton and other Obama Administration have made clear that the U.S. will leverage the allegations to convince the international community to impose further sanctions to pressure and isolate Iran.