Wisconsin primary as the race for the Republican presidential nomination heads into a critical stage, a new poll released Thursday reveals. Public Policy Polling's survey of 768 likely Republican primary voters shows Cruz leading by a whisker with 38 percent support, followed by Trump with 37 percent. But with the survey's margin of error of 3.5 percentage points, the two are in a dead heat, with either senator from Texas or the billionaire businessman in a position to capture all 42 delegates in the winner-take-all contest.