While Donald Trump seems slated to win a huge victory in Monday’s Iowa caucuses, The Washington Post’s Jim Geraghty says there are two variables that could make that expected win less likely for the former president. One is the weather, as Iowa officials are telling people to stay off the roads due to an incoming polar vortex — a development that has caused Trump and Nikki Haley to cancel campaign events. “With the polling making this year’s contest look like a Trump romp, maybe a portion of Iowa’s older Republicans won’t feel the need to get on the road and participate in the caucuses,” Gerag…