In Iowa Cruz has not only surged (as he has across the nation) but has surpassed Trump in most polls.
http://www.realclearpolitics.com/epolls/2016/president/ia/iowa_republican_presidential_caucus-3194.html
One of the interesting stories is the PPD poll released the same day as this poll 12-17-15 also has Trump over Cruz by about the same margin... 34% to 18%.
Yet question 24 asked "Who would you support if it came down to just Ted Cruz and Donald Trump... Trump 45% Cruz 44% and Unsure 11%.
http://www.publicpolicypolling.com/pdf/2015/GOPResults.pdf
45% to 44% is about as close as it gets....
Yeah, Cruz is surging.
Lets look at this poll...
One of the questions ask was to all voters.. Hillary vs ??? who would you think would win.
49% thought that Hillary would beat Trump and only 38% thought Trump would win.
Lets compare the same question to Cruz...
Cruz 45% vs Hillary 45%... virtual dead heat...
Trump is loved by many, but Cruz is too... and perhaps hated by less.
http://www.foxnews.com/politics/interactive/2015/12/18/fox-news-poll-2016-gop-race-trump-muslim-ban-terrorism-isis/
Also note that the trend over time shows Trump losing ground towards Hillary.. vs older polling times.
In Iowa, barely 2.5% of Iowans vote in republican caucus. It is hardly a primary. Santorum & Huckabee both won Iowa, only to be defeated in bigger states by Romney. Do not put all your marbles on Iowa.