Mitt Romney's Republican boosters are frustrated and infuriated, not just with their usual suspects in the mainstream media, but with their own presidential candidate.

And they have a right to be.

They believe Romney let President Barack Obama, the self-congratulating killer of Osama bin Laden, off the hook for its inexplicable handling of the murder by armed extremists of the American ambassador to Libya and three other government employees on Sept 11.

Serious questions have been building for weeks about that night.

It now seems clear that the Obama administration misled the American public by playing up the storyline that the incident in Benghazi was part of some spontaneous protest against the U.S., linked to the controversial video that was rocking the Muslim world at the time.

Rather than the planned assassination the administration now basically concedes it was.

It also seems pretty clear that there was a serious security failure, and perhaps an intelligence failure, on the night in question, as Romney claimed for a while, until he mysteriously stopped.

During the second presidential debate earlier this week, a member of the studio audience succinctly asked the president about the whole debacle. And yet, Obama escaped unscathed.

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Obama, outraged that Romney would challenge him over the death of an ambassador. But the administration may have more to answer to than it is letting on. (Reuters)

To the fury of conservatives, it was the debate moderator, CNN's Candy Crowley, who opened the door through which the president gratefully scampered.

That night and all the next day, Republicans hammered at the Benghazi exchange, calling it the most important moment of the night.

But then, late Thursday, after so much effort had gone into building a head of indignant steam, Romney himself appeared at two rallies in Virginia and didn't utter a word about the matter.

That evening, a Fox TV anchor asked, in a rather puzzled tone, why Romney was letting such an important issue go. It's a good question.

An act of terror?

For reasons that remain murky, it's also one that may remain unanswered.

Obama's senior officials have been evasive on the topic, and while it's unfair to call Crowley a lapdog, as some Republicans have – the woman is one of the smartest political journalists in Washington – even she has since admitted that Romney's concerns, which he attempted to voice in the debate, are "in the main" correct.

The Romney-Obama exchange began with a question Obama chose to dodge. Instead, he attacked Romney for playing politics with the issue.

Romney came back with a largely accurate, measured response, asking why Obama's administration took so long to acknowledge the attack was not spontaneous, but an extremist assault.

Obama, indignant, replied that the very next day, on Oct. 12, he had appeared in the Rose Garden and denounced the attack as "an act of terror."

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State Department official Charlene Lamb testifies at a congressional hearingabout the September 11, 2012 attack on the Libyan consulate in Benghazi. Diplomatic security in Libya was drawn down ahead of last month's fatal attack and U.S. officials did not have enough protection, former head of a U.S. security team in Libya, Lieutenant Colonel Andrew Wood, told lawmakers on Wednesday. (Jose Luis Magaua / Reuters)

When Romney tried to disagree, Crowley jumped in, straight-armed Romney and said the president was correct and that it was time to move on. Obama, delighted, asked her to repeat that, and she complied.

But while Obama did indeed use the word "terror" the day after the attack, and again on Sept. 13, at a political event, it was an indirect reference.

On the day of the incident, the president directly called the Benghazi attack "senseless violence," then went on to recall that it took place on the anniversary of 9/11, concluding with a general denunciation of "acts of terror."

And in the days that followed, his administration, for some reason, embarked on a concerted effort to blame the killings on the amateurish anti-Muslim YouTube video that had triggered protests at Western embassies worldwide.

Obama and his team repeatedly denounced the video, no doubt seeking to distance Washington from it as much as possible.

The most prominent administration messenger was Susan Rice, Obama's ambassador to the U.N. "What sparked the recent violence was the airing on the Internet of a very hateful very offensive video that has offended many people around the world," Rice told Chris Wallace of Fox News on Sept. 16, four days after Obama's Rose Garden remarks.

She explicitly said the killings in Benghazi were "a spontaneous reaction." And the White House spokesman, Jay Carney, was putting out the same line.

It was not until Sept. 20, nine days after the killings, that Carney finally told reporters that what happened was "an act of terror." Which is what some Republicans, notably John McCain, had been saying all along.

Why the discrepancies?

More recently, stories began to surface that in the weeks before the attack, the State Department had turned down requests that a military security team deployed in Benghazi be extended.

About a week before the second presidential debate, Republicans called current and former State Department employees before a House committee to explore those stories and found they were true.

The night before that hearing, a senior State Department official conceded during a background briefing with journalists that not only was the Sept. 11 attack in Libya not spontaneous, there had never been any public protest of the anti-Islamic video in Benghazi that day.

The attackers had shown up on a mission to kill. The killings were far from "senseless violence," as the president put it on Oct. 12.

Why the discrepancies? The administration has offered no clear explanation. Vice-president Joe Biden has blamed erroneous information from security officials. So, now, does Susan Rice.

But that doesn't square with reports the day after the killings, evidently emanating from intelligence briefings to lawmakers, that the attacks were military in nature, and employed heavy weapons, which several journalists, including me, reported on Sept. 13.

There, are, however, clues on the public record as to why the water remains so muddy. It is clear, for example, that the CIA was well ensconced in Benghazi, operating from an "annex" near the diplomatic mission. Eastern Libya is known as the country's Islamist centre.

There have been reports that several U.S. intelligence agents were evacuated shortly after the killings. It's hard to imagine they aren't back by now, with their own paramilitary protection, and anxious that their presence in Libya remains undisclosed.

Read what you will into Obama's icy glare during Romney's attempt to question him on why it took so long to admit there'd never been a demonstration in Benghazi on Sept. 11, but Romney has been receiving confidential intelligence briefings for weeks now, and the president would know what he's being told.

Again, it's conjecture, but that might explain Romney's silence on the Benghazi matter the day after the debate.

Nonetheless, it seems pretty clear that the White House deliberately misled the public about the attack in Benghazi, either for security reasons or perhaps for political ones.

The Benghazi attack appears to undermine a central Obama campaign boast that al-Qaeda is "on its heels," if not a conquered force.

Many Republicans now want Romney to press this case in the final debate on Monday, which will be devoted entirely to foreign policy.

If Romney does, and the president is not given an escape hatch by the moderator again, it will be interesting to hear his answers.

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Obama and Romney, with debate moderator Candy Crowley, a veteran CNN reporter, on Tuesday night. (Reuters)