Can you link us to one? Seriously.
Fine, let me google that for you:
http://www.wnd.com/2016/05/rafael-cruz-finally-responds-to-trumps-oswald-allegation/
http://www.dailymail.co.uk/news/article-3556745/Ted-Cruz-furiously-denies-latest-claim-tabloid-claims-identified-dad-photo-Lee-Harvey-Oswald.html
https://www.yahoo.com/news/cruz-to-trump-my-father-is-not-linked-to-jfk-165004201.html