some kind of exclusion based on one's faith or the lack of faith, frankly. >> ben carson will be campaigning later this morning in ohio. you can be sure this controversy will follow him there. muslim groups have called on him to step aside. he's rejected those calls, of course. this episode is defining his candidacy right now. it's one more thing, alisyn, republican leaders sure wish they weren't talking about in this presidential campaign. scott walker trying to persuade trailing candidates to follow his lead and drop out of the race. this as two gop candidates hit late night television. cnn's athena jones is live in washington with the very latest for us. good morning, athena. >> reporter: good morning, alisyn. walker is the second candidate to drop out in less than two weeks. he's less the second one to do so while taking a swipe at the front-runner donald trump. walker had been seen as a real contender just a few months ago. and now he says he's pulling out of the race for the good of the party.