Fair enough. You know a lot more about this than I do. I don't have a ton of confidence in Trump's Fed, but I'm also not sure which chairs are up and when.
Thing about deflation is that it would normally require companies to prefer to sell at a loss than stack inventory. That isn't likely to happen, and it's voluntary. Inflation, to some degree, is not, right? If I run a business and my employees are demanding a 5% wage increase and my supplies cost me 5% more, I have to pass along at least some of those costs. My hand is forced. But nothing forces me to unload inventory at a loss.
With this insight, you can infer that deflation will happen under one of two conditions:
1. Actually deflationary monetary policy, like raising interest rates (i.e. contractionary policy) in a recession. That isn't going to happen. Even if Trump were to put a loyalist in charge the Fed, Trump himself loves low interest rates. In the Great Depression, this deflationary monetary policy was created automatically by the gold standard. And note that the Depression was the only period of anything approaching sustained deflation in the last hundred years, unless I'm forgetting about something.
2. Things that force the sale of inventory, like systemic liquidity constraints. That's why we flirted with deflation in '08 -- when the banks were calling in all their revolvers, companies were having trouble getting financing for stacking inventory. So they would have to sell at a loss, or go bankrupt (which would likely end up with selling at a loss).
Now I suppose it's possible that we could have a banking system collapse under horrible policies, but no vector for that comes to mind. Like, things would have to really, really go south and I think even Trump would have trouble causing that much damage in that short a time.
3. The other wild card would be if Trump wants to default on US debt. I would hope that everyone would be getting in his ear telling him not to do that. It wouldn't be in his financial interest to do so (he would probably lose all of his properties, unable to secure any financing). Maybe he really is the Joker and he affirmatively wants complete chaos, but otherwise . . . it's possible, I suppose. It does worry me.
So could deflation result from a US debt default? I have no idea. It's really hard to game out this scenario because there are multiple equilibria. It's possible that the default could create a financial panic, which usually results in a flight to safety, and historically that has meant a flight to the dollar. So it would be weird if the US defaults and then sees the price of its bonds increase, but that's a possible outcome if the market believes that the US would correct course. But it's not guaranteed. There could be a flight to safety to other currencies, especially Euro. This depends mostly on the market's perception of the Euro, which is hard to predict.
In either case, the market can create a temporary safe haven if all the money flows the same direction. So we'd get a lot of volatility and then maybe some new status quo would emerge. But that's by no means guaranteed. Meanwhile, it's hard to predict what would happen to the financial sectors round the world, and that could create a feedback loop.
I would even be possible for the market to shrug it off. I don't think this is likely, but the logic goes like this: securities are priced as the (risk free rate) + some spread measured in basis points. The spread can be credit quality, currency risk, counterparty risk, etc. Now, what happens if the risk free rate turns out to be not risk free? Yikes. Every security would be mispriced. It would be such a catastrophe that traders might go on as if nothing happened. Here's an analogy: suppose you were at work at an office in DC when you overhear someone saying that the Russians had just launched their nukes. What would you do? What I would do is to keep doing what I was doing. If the bombs are actually on their way, I'm dead regardless. And if the bombs aren't actually on their way (or they had been picked off by some defense system), then I should do what i want to be doing at that moment, which presumably would be what I was doing. The default on US debt could be a little bit like the Russians launching. It could wipe us all out, or it could be corrected.
I should add that I haven't followed finance theory for the past few years, so there might be recent work done on this topic that I'm not aware of. I mean, even a decade ago people modeled the scenario and produced estimates of what could happen, but I never saw any reason to prefer one model over the other. There's no historical guidance. And in multiple equilibria games, the game can tipped one way or another by really small factors. I wouldn't say it's chaotic in a chaos theory type of way (though I have seen that argued), but it would be hard to predict which of the thousands of possible variables might be determinative alone or in combination. Again, it would depend on market psychology. But it's possible that the models have improved.
For my part, I developed a system to prevent the US from defaulting on the debt. Politically unrealistic, but it would probably work. I was going to publish it in a law review, but I couldn't find a taker because it didn't have too much law in it. So I was going to revise and resubmit, but then Trump won in 2016 and I became depressed and then found myself increasingly unable to find any enthusiasm to teach law in a world less and less defined by law.