Did Intrade correctly predict the 2008 Presidential Election?

The answer is - without a doubt.  The Intrade prediction market was forecasting a sizeable Obama victory for most of the election season, and correctly predicted the results of nearly every state in the Union.

Shown below is a graph which uses the state-by-state betting data from the Intrade prediction market.  The graph shows the total number of electoral votes Barack Obama was predicted to win from late May until election day.  States had to be trading above 55 on the prediction market to count toward the total number of forecasted electoral votes. 

Barack Obama was predicted to win over 270 Electoral votes (the winning threshold) for most of the election season, except for a few weeks during the late summer.  Once the sub-prime lending mess began to unravel on Wall Street, Intrade predicted an overwhelming victory for Senator Obama.

Shown below is the same chart for Senator McCain.  At no time during the entire election season was John McCain forecasted to win 270 or more electoral votes.  Immediately after naming Alaska governor Sarah Palin as his running mate McCain saw a brief surge in his forecasted EV count, which quickly dissipated.  Senator McCain consistently found himself in the position of needing to win every single swing state to be able to secure a winning 270 electoral votes.

There was only one point in mid-September when McCain was actually forecasted to win more electoral votes than Obama.  Other than that, Obama enjoyed a sizeable lead for most of the election season.  Shown below is a graph of Obama's lead over McCain during the election season.

See Also:  Intrade compared to the polling data