Within the past week, both Mike Huckabee and Donald Trump announced that they would not seek the Presidency in 2012. The prediction markets had plenty to say about these candidates both before and after they dropped out of the running. Both men's likelihood of winning the Republican nomination peaked at nearly 9%, but the markets show that the end of their campaigns came about under very different circumstances. Below is a chart of Mike Huckabee's likelihood of winning the Republican nomination, where the red line marks the moment when he made the announcement he was not running during his weekly Fox News TV show. One day before his on-air announcement, when rumors of an impending announcement on his campaign began to spread, this market tanked rather quickly. The market was reasonably quick to recognize that he was going to drop out of the race. However, it appears as though the market began to second-guess itself over the following 24 hours – perhaps due to conflicting rumors – and by the time of his announcement, the Huckabee contract regained about 1/3 of the value lost during the previous day.
Donald Trump's likelihood of winning the Republican nomination peaked just before President Obama released his long-form birth certificate on April 27, and began its precipitous decline just as Obama announced the death of Osama Bin Laden on May 1. The final drop on May 17 coincided with his announcement that he will renew his job as a television personality, rather than run for President. While Huckabee was an extremely viable candidate prior to his announcement, Trump had already been trending towards irrelevancy, even before his announcement.
I regret that we had not been tracking Jon Huntsman's chances until very recently, but the other two candidates who clearly benefited the most probability of victory with the Huckabee announcement were Mitt Romney and Tim Pawlenty. As I note in the first chart there are really two separate noteworthy events in Huckabee's withdrawal from the race. The first occured when rumors of an impending announcement were circulating and the second occurred a day later when his decision was announced. The first reaction of the market was to assume that Romney was going to really benefit from Huckabee's departure. After the rumors began, going into the formal announcement (where the red line is located), Romney had absorbed almost all of the Huckabee's total loss. Yet Romney gained little from the formal announcement while Pawlenty, who had already fallen back down to his pre-rumor level, got a nice boost from the actual announcement. One thing is clear from this analysis: the market is undecided on who benefited from the Huckabee announcement.