one candidate received the endorsement of former president trump. tuesday s vote is being seen as a test of mr. trump s power over republican voters jesse kirsch is with the candidates in ohio. that s why we need to finish donald trump s border wall. reporter: tonight ohio s republican senate primary testing former president trump s vice grip on the gop. he endorsed author jd vance along with other conservative headliners, but they haven t thinned the field. with just two days to go if jd vance is not successful next week, what does that say about th clout of donald trump. we don t want a circumstance where they could defeat president trump. so if president trump s brand is on the line, the maga brand is on the line. reporter: vance surging to first in a fox news poll, but within the margin of error. josh mandel is in second, not backed by trump. but still tieing himself with the former president stumping with texas senator ted cruz the name trump is much more an endorsement.