After McCain announced Palin as his co-driver for the Straight-Talk Express, the polls and the markets that were tracking US public opinion went berko. Between September 2nd and September 8th, the Gallup daily tracking poll made a 13 point turnaround — with Obama plunging from his 8 point margin over McCain to being five points behind in six days. and, the two premier US polling analysis sites, both showed the State polls reacting massively to the McCain/Palin ticket and the Intrade markets at both the headline and the individual State levels plunged dramatically for the Democrats.

Obama went from 311 expected Electoral College votes down to 270 in the 11 days following September 8, with his headline probability of victory plunging from 61% down to 49% on the Intrade headline market, and from 65% down to 50% probability using our State market simulations. Visuals work best here to show the enormity and the speed of the movement.

Yet while the Obama plunge was dramatic, the recovery has been no Sunday drive in the country either, with Gallup showing a seven point turnaround in the last week, now having Obama back in the lead with both the headline and State Intrade markets similarly moving the Democrats way.

Whatever things may be said about the US election, certainty of victory for either party is simply not one of them. Volatility in the polling and the markets is the name of the post-convention game.

Our State simulations (which, if you’re a nerdy type you can see all the gory details of over here) reacted less to the national polling plunge in terms of their expectations of a Republican victory than did the headline Intrade market, and with today’s latest round of State based polling suggesting that the States are creeping back towards the Democrats — the State Intrade markets still seem to be the leading electoral metric to keep our eyes on in terms of where this contest is heading.

If you were a candidate, you’d still prefer to be in Obama’s shoes rather than McCain’s, especially with both the polling and markets trending back toward the Democrats — but with the Wall street chaos sweeping through both campaigns and the US public getting a little nervous, it might only take one gaff, one killer advertisement, or one misspoken truth for either candidate to irreparably damage their chances at becoming President 44, especially with an electorate that seems to be so flitty.

*Possum Comitatus’s blog Pollytics is now featured as part of Crikey’s blog network.