Seventy percent of Intrade Market bettors are wagering that Mitt Romney wins the April 24 Pennsylvania Primary. I think he will, too, purely based on his campaign organization.  To me, that strongly suggests that native son and former Keystone State senator Rick Santorum will exit the presidential contest soon before April 24th. Losing in Pennsylvania would be a blow that Mr. Santorum — who is only 53 — might never recover from.  He has done too well this primary season to let that happen. 

Mr. Santorum exiting pre-Pennsylvania could be what is keeping Newt Gingrich’s toe wistfully in the race. Perhaps he is betting, too, that Santorum will drop within a month. No one is betting on Mr. Gingrich for anything, though. His campaign all but ended weeks ago. When Rick Santorum capitulates, the race is over.