republicans raising questions, all over whether cruz could face a legal challenge. he was born in canada but his mother was a u.s. citizen. trump told wolf blitzer that cruz's birthplace raises constitutional concerns. >> there's this doubt. people have doubt. you know, i want to win this thing fair and square. i don't want to win on this point. >> reporter: john mccain once calling him a wacko bird. mccain himself was born outside of the united states and was quick to distance his case from cruz's, as he was born on a military base. >> i'm not a constitutional scholar on that but i think it's worth looking into. >> reporter: in iowa, cruz brushed away trump's comments. >> it's no surprise that they are going to jump on with the silly attacks as we get closer to election day. >> reporter: cruz, one of trump's biggest threats, says