Mitt Romney's odds of winning Wisconsin, which holds its primary alongside Maryland and the District of Columbia on Tuesday, have been very good for about 10 days, according to both the political prediction markets and the major polls. We are very confident that he will win Wisconsin, where his odds currently sit at 96.2 percent. Rick Santorum is just 4.3 percent likely to pull off an upset victory. Romney is also almost certain to carry Maryland.
Sources: Betfair and Intrade for prediction market data and FiveThirtyEight for poll-based forecast
What the polls don't tell you is that contrary to his dismal numbers in mid-March, he's always had at least moderately favorable odds in the state. We should remember, however, that markets use polling data just like everyone else, and aggregate that information with other signals to produce their odds. The big jump we see in the odds correlates with the release of positive poll numbers for Romney.
Santorum and the other candidates now have negligible odds of winning the nomination. There is a small but non-negligible likelihood of a brokered convention, but Romney would likely emerge as the nominee, given that he will control the most delegates.
Republican voters know that giving Romney momentum heading into the summer is valuable for his likelihood of defeating President Barack Obama. Voters inclined to support Santorum, Ron Paul or Newt Gingrich are now weighing that potential boost to their party's odds in November with the value of sending the signal of their support for one of the other three candidates. It is not inherently clear which is a more rational vote, but Romney does not need too many of such voters to switch to his camp to accumulate enough delegates to seal the deal before the convention.
A slightly closer contest is occurring tonight in New Orleans: Kentucky is 73.3 percent likely to win the NCAA Final Four over Kansas. Follow along in real time with PredictWise for the NCAA Championship and Republican primary contests.
David Rothschild is an economist at Yahoo! Research. He has a Ph.D. in applied economics from the Wharton School of Business at the University of Pennsylvania. Follow him on Twitter @DavMicRot and email him at firstname.lastname@example.org.
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