From Arianna Huffington

It was the economy, stupid. It was the Latino/African American disconnect. It was the media finally giving Obama some heat. It was Saturday Night Live (all hail Amy Poehler, Lorne Michaels, and Jim Downey — political kingmakers).

But the real answer is to be found deep in our lizard brains. Clinton won by dealing from the bottom of the deck — and the bottom of the barrel — and playing the fear card. And, as happened in 2002 and 2004, Be Very Afraid proved to be a very effective campaign pitch.

After her New Hampshire comeback, Clinton famously declared: “I found my own voice.”

For this latest comeback, she found Karl Rove’s voice.

People aren’t currently stocking up on Cipro and duct tape but, as the cable channels’ hyped up reaction to the Times Square explosion showed, these are still jittery times. And appeals to voters’ lizard brains still move the needle.

After an 11 state losing streak, Hillary Clinton didn’t suddenly transform into a more compelling candidate. Only a spookier one.

So we got the 3 a.m. phone call, making no real argument about preparedness to lead, only the shadowy insinuation that bad things will happen to your kids if you vote for Obama. Trailers for slasher movies have less of a creep-you-out factor.

We got Hillary’s ready-to-lead scorecard: “I think that I have a lifetime of experience that I will bring to the White House. I know Senator McCain has a lifetime of experience to the White House. And Senator Obama has a speech he gave in 2002.” This scorched earth pronouncement led Air America’s Rachel Maddow to tell Keith Olbermann, “That’s what you say when you want to be John McCain’s vice-presidential choice. That’s not what you say when you’re trying to become the Democratic nominee for president.” Olbermann’s take: “Unbelievable.”

And we got that jaw-dropping moment on 60 Minutes where Clinton generously announced that she takes Obama at his word that he’s not a Muslim and rejected rumors that he is with the so-big-you-could-fit-a-madrass-in-it caveat, “As far as I know.” What’s next, “Obama is a human being… as far I know”?

It’s worth remembering that earlier in the campaign, when Clinton was still pitching the inevitability of her candidacy and fending off attacks from her opponents, she roundly disavowed these kinds of tactics. “I’m not interested in attacking my opponents,” she claimed in Iowa in November. “I’m interested in attacking the problems of America and I believe we should be turning up the heat on the Republicans.” Terry McAuliffe reiterated the do-no-harm-approach: “We’re going to focus on the Republicans. We’re going to focus on winning the White House. We’re not going to attack our fellow Democrats. That’s not what we want to do.”

That is, they didn’t until the high road looked like it would turn into a dead end. Then out came the fear-mongering playbook and the phone started ringing at 3 a.m.

I’ve written before about how fear-mongering works, causing voters to react not with their linear and logical left brain but with their lizard brain and their more emotional right brain.

Deep in the brain lies the amygdala, an almond-sized region that generates fear. When this fear state is activated, the amygdala springs into action. Before you are even consciously aware that you are afraid, your lizard brain responds by clicking into survival mode. No time to assess the situation, no time to look at the facts, just: fight, flight or freeze.

When we are in this state, we are biologically programmed to pay less attention to left-brain signals — indeed, our logical mind actually shuts itself down. Fear paralyzes our reasoning and literally makes it impossible to think straight. It’s the neuroscience, stupid!

After Tuesday’s success, you can be sure the Clintons’ march through the mud will continue over the seven weeks until Pennsylvania. Bill Clinton understood the potency of playing to voters’ lizard brains — it’s why he started rolling the fear dice back on the Charlie Rose show. How to counter this kind of fear-mongering without kicking off a round of Mutual Assured Destruction for the Democrats is the Obama campaign’s greatest challenge.