In my previous post, I suggested that the proper historical comparison for Trump, should he become president, is Jimmy Carter-- the outsider who wins despite a lack of good relations with his own nominal party, and no understanding of how Washington actually works, thereby stymying any attempt to change policy through normal means. Republicans in Congress hate the guy, and most executive branch employees have "civil service" protection that would prevent Trump from going around and saying, "you're fired!" to bureaucrats who refuse to play along with him. What could Trump really do?
1) The Wall. Can it be built? Yes. Will Mexico pay for it? Do I have to dignify that question with an answer?
If a Republican majority gets the House and the Senate, will they pass a bill to build the wall? The complication is whether or not Mexico footing the bill is a precondition. If yes, the wall doesn't get built. Contractors won't take the job on the promise of getting paid when Mexico ponies up the money because everyone with a brain knows that will never happen. On the other hand, nothing will stop Congress from appropriating the money, if they choose. It would cost a lot. A big fence? Maybe. A wall? Depends on how much Congress wants to spend.
2) A trade war? Trump has been sounding like a protectionist, with promises of tariffs and other stuff.
Starting a trade war cannot be done by executive order. It would require congressional action. Republicans in Congress are split between protectionists and free-traders, with the divide roughly matching the one between the Chamber of Commerce faction of the party and the social conservatives. The former won't back any trade war.
Trump likes to say that we don't "win on trade." The whole point of trade, though, as anyone who has read Adam Smith can tell you, is that there is no such thing as a "loser" on trade. A business transaction makes both participants happier. That's the point, and the basis of the invisible hand. The seller prefers the money to the product, the consumer prefers the product to the money, so everyone is better off.
Well, maybe not everyone, but here's the problem. If we are running a trade deficit, who benefits most? Consumers. We get cheap goods. Who does worse than without trade restrictions? US producers, because we are buying cheaper goods from foreign producers. Impose trade restrictions, and consumers pay higher prices, with business going to US firms. Is that worth it?
Make up your own mind. The important point, though, is that trade restrictions hurt plenty of people in the US. Will Congress play along, knowing that? Not bloody likely. There won't be a trade war because the president can't start one unilaterally, and Congress wants no part of one.
3) A shooting war? Speculation among Trumpophobes is that he might throw one of his patented temper tantrums over some imagined slight by a world leader, and get us into a shooting war.
Only Congress can declare war, but the president has plenty of authority independently of Congress. Under the war powers resolution, the president has a couple of months with which to do pretty much anything he wants with the military. And, even after that, Obama has stretched the bounds of war powers so much with Libya that there are essentially no legislative constraints anyway.
The real constraint is the military. Hypothetically, let's say Justin Trudeau makes a joke about Trump's tiny, tiny... hands, and Trump orders the Army to invade Canada. Cue music. Would the generals actually follow through? If the scenario is that ridiculous, they may not.
On the other hand, could he spend months drumming up sentiment to invade Mexico if they don't agree to pay for his wall? Well...
Trump is unpredictable. The probability here isn't zero. Nuking France because a French MP made a comment about Trump University? No. Let's be realistic. It's fun to joke about this stuff, but it won't happen.
4) Rounding up Mexicans, muslims, etc.
This is the scenario that Trumpophobes really mean when they compare Trump to Hitler. There are both legal and practical obstacles. When FDR issued an order to intern Japanese-Americans, he justified it under wartime powers. Without a declaration of war, which Congress is unlikely to issue, the legal structure just isn't there. Of course, presidents don't always follow the law. But, there are big legal obstacles to having the US military operate on US soil. And the generals know it. Would they actually follow such an order, without a formal declaration of war? Your answer to that depends on how much you trust the generals' basic intelligence. Even if Trump were to issue such an order, for the generals to actually follow it would be really fucking stupid.
And this is precisely why Trump is unlikely to do it. A private advisory session would make it clear to Trump that such an order wouldn't be followed because the generals a) know the law, and b) know the consequences if they follow this kind of illegal order.
Will Trump order the rounding up of Mexicans, muslims, and anyone who makes jokes about the size of his hands? No. Calm the fuck down.
We have a very different legal and political structure from Germany. Checks and balances, a distinction between the military and domestic law enforcement, etc. This is why the proper historical comparison for Trump is Carter. Read your Nelson Polsby.
What would Trump do as president? I really don't know, and neither does anyone else. I doubt even Trump knows. A bad president can do a lot of damage, and Trump is a reckless, undisciplined person. But let's not get carried away with ridiculous scenarios.