specifically, the common core standardized tests. so far this year, more thanea 250,000 students across thes country have opted out of taking the tests, which measure proficiency in math and language arts. julianna goldman now on how the common core debate is playing out on the campaign trail.ra >> reporter: with parents andac teachers protesting what they say are burdensome, confusing, and time-consuming standardizednd tests, common core is emerging as a key issue on the trail. >> common core is an issue very close to my heart. i want to know your stance on common core. >> reporter: and it's forcing presidential hopefuls to navigate politically-fraught terrain right out of the gate. >> high standards assessed the right way combined with real accountability is what we need. >> reporter: former florida governor jeb bush has been a bee staunch supporter of the program but yesterday in new hampshire he emphasized that participation is voluntary. >> here's what we don't need--