Donald Trump and Ted Cruz running neck and neck in the upcoming 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.Ohio Gov. John Kasich, who has been trailing in third place behind Trump and Cruz, garnered a weak 17 percent in the poll.In a Trump-Cruz matchup without Kasich in the mix, Cruz leads 49 to 41 percent in the Badger State primary which will be held next Tuesday.As of Thursday, Trump has won 752 delegates, Cruz 463 delegates and Kasich 144 delegates. It takes a total 1,237 delegates to win the nomination straight out, without the need for a contested convention.The Public Policy Polling survey was conducted March 28-29.