I set out in some detail on December 25th "Cruz Decline Underway?" that there were clear signs that Senator Cruz's ascent had begun its descent or had, at least, reached its maximum point.
This was in respect to his nationwide polling but subsequently his key primary states of Iowa, where he had overtaken Donald Trump, and new Hampshire have begun a decline and his nationwide polling confirms he is in decline there as well.
This reflects Donald Trump's uncanny ability to identify who is his most dangerous rival at any given point and his beyond incredible ability to mount a successful plan of attack which is sharply focused on one aspect of his rivals failings.
With Carson it was his personal history which was confused to say the least, with Bush his "lack of energy" and with Cruz, and with seeming perfect timing, his constitutional right to be president.
"Iowa Gov. Terry Branstad said today the issue of whether Ted Cruz is legally eligible to run for the presidency is “fair game”
"Harvard scholar: Ted Cruz's citizenship, eligibility for president ‘unsettled’
That major voices echo Trump's Cruz comments just before the Iowa election is beyond being put down to just "good luck" it marks Trump as someone out of the ordinary which is why commentators liek Philip Bump and Dana Milbank have been left floundering in his wake and Nate Silver destroyed as a one trick G.W. Bush/Obama pony "pundit.
New Gravis OANN Poll January 10th of 832 Republicans with a margin of error of +/- 3.4% Gives Trump a huge 21 point lead and confirms the Cruz RCP average of 20%
In head to head polling Trump has a two point lead as good as any other GOP candidate against Hillary;
REAL CLEAR POLITICS LATEST NATIONWIDE POLL. CRUZ'S PEAK WAS DECEMBER 20TH
(BLACK) NATIONWIDE TRENDLINE FOR CRUZ
(BLACK) NEW HAMPSHIRE TREND LINE FOR CRUZ
LATEST IOWA POLLING
The spearhead right to the heart of @ppppolls Dean Debnam & all lib's
IOWA TREND LINE FOR CRUZ