Gut v. Head
In attempting to aggressively to shape the political afterquakes of Benazir Bhutto’s assassination to their closing argument, the Obama campaign may have deliberately violated their “Never Let Them See You Sweat” rule.
The Clinton campaign wanted to let the story speak for itself, betting that the general atmospherics are more potent than the specific type of precipitation – that anything that speaks to the need to have a credible Commander in Chief helps her, even when the specifics – a resurgent Al Qaeda, Middle East chaos, -- might remind Democrats of her war vote. It's a distinction between gut and head; if you're a Democrat, your gut sends you to safe harbors; your head sends you to the candidate who got it right.
If the atmospherics benefit Hillary Clinton, it's because the assassination itself is less important to voters than the general feeling of instability that emanates from the Middle East; War is the ultimate existential threat. Nuclear terrorism is the existential threat of our age.
If the atmospherics benefit Barack Obama, it's because voters went beyond their gut feelings and engaged their brains; listened to Obama's argument and then recalled their anger (another emotion!) at Democrats in 2002.
If you want to know why pundits are suggesting that Clinton might find the circumstances more congenial, it's because an affective response is instantaneous, and an affective response like fear is usually indelible; it takes a few more microseconds for that prefrontal cortex to engage, to call on those arguments stored in the hippocampus, and to cogitate.