Ted Cruz has opened up a firm lead over rival Donald Trump in first-in-the-nation state Iowa, 31 to 21, according to a new Bloomberg Politics/Des Moines Register poll released Saturday. The poll is closely watched by political analysts who consider it a reliable measure of Iowa caucus voters..... Cruz's ascension represents the largest spike for one candidate between Des Moines Register polls in at least the last five presidential elections. Though fifth overall, Jeb Bush records the highest negative ratings in the poll, with 54 percent of likely Caucus-goers disapproving of him....