In less than 30 days, actual votes will finally trump the polls in one of the most unpredictable presidential races in recent memory, marked in large part by the sudden rise of a brash-talking political phenomenon known as The Donald. “No one absolutely has to win Iowa, but it would be very helpful for both Trump and Cruz. They’ll have to explain why they lost, if they do. The others have an excuse: ‘We weren’t expected to win anyway,’ ” said Larry Sabato, a political scientist at the University of Virginia.