Over the past couple of months, I’ve had the opportunity to discuss foreign-policy issues with Wisconsin governor Scott Walker. Beforehand, I didn’t know him personally and so didn’t know what to expect. Well, here is what I found: Walker has the potential to be a great foreign-policy president. Here’s why. The first thing I learned is that Scott Walker is eager to talk about foreign policy. He relishes discussing the ins and outs of an issue and shows a curiosity that frankly I wish many of our senators had. He engages precisely at the level a president should, asking tough...