Did Rick Santorum really just come within a few micro-seconds of calling America's first ever black president a "nigger"?

Of course not, comes the rational response. Apart from the fact that it would instantly be a campaign-killing gaffe, it would be in direct opposition to the Santorum image we have seen now for months. This is the man who is almost too goody-two-shoes to be real. He has a large and loving family. He may be ultra-conservative, but he also appears to be the sort of suburban dad who would be more likely to say "Aw, shucks" and "Jeepers creepers" rather than deploy the most offensive word in the English language. He wears sweater vests!

But about that video. What is going on there?

Santorum was speaking at a rally in Janesville, Wisconsin, still locked in the ferocious nomination battle with Mitt Romney and still desperate to become the true conservative standard-bearer of the Republican party.

"We know the candidate Barack Obama, what he was like – the anti-war government nig …" he seems to say, then suddenly stopping, and changing tack to add: "America was a source for division around the world, that what we were doing was wrong."

It is hard to think of exactly what word Santorum was about to use. What word beginning with "nig-" comes naturally after government? It has been suggested he was trying to say "-nik", as in peacenik or beatnik. That is possible. Or perhaps, it was some non-specific verbal tic: a random vowel-consonent flub.

Here, Santorum has previous form. In Iowa, he stumbled when discussing conservative opposition to welfare programmes:

"I don't want to make black people's lives better by giving them somebody else's money; I want to give them the opportunity to go out and earn the money."

In the face of later outrage at singling out black Americans, he insisted that he had not said "black", but instead vocalised "bleugh", as his mind became confused over his own train of thought. Believe that? Judge for yourself here.

Santorum and his campaign have continued to vociferously deny he said "black" in Iowa. Personally, I don't believe him. The video seems clear enough to me.

Santorum's team have also denied that he intended to say "nigger" in Wisconsin. In this case, I am much more inclined to give him the benefit of the doubt. The video is odd: his exact meaning, and even the nature of his stumble, is unclear. For a candidate who frequently makes a great play of the fact that, unlike President Obama, he does not use a teleprompter for his stump speeches, his slips-of-the-tongue are becoming a liability that should make him think twice about extemporising.

But giving Santorum a pass in this instance masks a larger point. The GOP nomination race has seen Barack Obama consistently painted as a radical, a danger to the American way of life and someone out to fundamentally transform the country. And that is just by the candidates. Among the audiences at Republican rallies, the overheated rhetoric and demonisation have been more lurid still.

Just as he has been since the summer of 2008, Obama is consistently accused by some GOP supporters and Tea Party fans of being a Muslim, a communist or a terrorist (or sometimes, all three). The argument over the place of his birth still burns brightly on the right, despite the proven fact it was Hawaii.

It does not take a great leap of imagination or sophisticated academic insight to see a racial fear of "the other" in all of this stuff when it is said about the history-making figure of a black president in the White House. Nor is this limited to the people who attend rallies. There is a long list of minor Republicans and conservative figures who get caught out for staggeringly crass racial comments around Obama. To name a few:

The head of the college Republicans at University of Texas who tweeted: "My president is black, he snorts a lot of crack. Holla."

Or the blogger for the conservative John Locke Foundation who posted a picture of Obama in drag with a bucket of fried chicken on the group's website.

Or the Orange County Republican official who circulated an email that featured Obama as the child of chimpanzees.

Or the Republican city mayor in California who circulated an email with a picture of the White House lawn turned into a watermelon patch.

There is simply a lot of this stuff about. Now, I am willing to believe that Santorum had no intention of saying "nigger" when he stumbled in Janesville. Perhaps he did mean to say "government-nik". Perhaps his brain just froze. It happens.

But it is no surprise to me that others will think the worst of him. After all, plenty of Santorum's fellow Republicans and conservatives have given people ample reason to do so.