Denounce the TPP at the top of his lungs, which I believe he's already started on. It'll quite nicely rebuild his populist credentials, and set him apart from most of the clown car.
Very much so.
Also: He should take a Kasich line on Iran while advocating ways to get us out of the Middle East quagmires. He should discuss how we shouldn't be there in the midst of squabbles, while emphasizing that these squabbles (many of them, anyway) have little to do with VITAL American interests.
He should also blast Fiorina as an irresponsible warmonger. He should call her out, and state that peace occurs when we talk to our enemies and find common interests. He shouls point out that this is what Reagan did. He should also point out that Reagan NEVER refused to negotiate with the Soviets and NEVER engaged in pre-emptive wars. After all, says Trump, the REAGAN foreing policy made America great, while the Bush 41 and Bush 43 foreign policies shot this country to hell.