The slight consolation I get as global temperatures keep climbing is that I'm winning my bets on the issue. So how about the same for Trump. I need bets based on what Trump has promised or described, bets that have some objective basis for measurement. I'd like the bets to pay off at the beginning of 2020, so they play some tiny role in the 2020 election (assuming we have one).
Coal seems like an obvious one. Brad Plumer has a good explainer on Trump promising he'll "put our coal miners back to work" and why that's a lie. Clinton at least had a $30b plan to help transition coal workers. Trump's plan is to eliminate environmental regulations - might help the company owners make some money and even slow the loss somewhat, but doesn't help or pay for a transition.
I've got $5,000 that says coal employment at the end of 2019 will be lower than the day Trump is inaugurated. He doesn't have to bring a single job back like he promised, just stop the slide. Actually I'll make it even better - if he keeps the slide to no more than 2% a year on average, 6% total loss, then I'll fork over $5k. (UPDATE: I think it's reasonable to address the optics question that David Appell raises in the comments. I will note the bet premise is that coal workers would be better off if they supported Clinton, although the coal CEOs would not, and betting is a way to demonstrate that prior to the 2020 election. But to avoid any misunderstanding, I've always been open to having my bets directed to charity instead of personal enrichment of the betting parties. Let's make this one's payment directed to charities in coal country - my direction would be for a charity helping transition away from coal, my opponent could choose whatever suitable direction he likes (it's going to be a "he" if it's going to be anybody).)
For Obamacare, I'm trying to think of an objectively-determined outcome to bet over - let's say that if Republicans repeal or repeal/replace Obamacare before the end of 2019, the percentage of Americans with health care coverage through private or governmental plans will drop. Defining this may be a bit difficult - it would have to be something rejected by most Democrats, not a grand deal. It would also have to be more than a fig leaf - I could see Trump and pals making a small change to Obamacare and present it as revolutionary fix. Good outcome, but not a test of Republican versus Democratic policies. So that bet might need an umpire. $5k on offer.
And finally, climate change isn't a hoax. Hard to test that in a short period of a few years with all the variability, but sea level looks like a higher signal-to-noise ratio. Lets make it four years, July 2016 to July 2020, I put up $5k at 2:1 odds that sea levels will be higher at the end. Details TBD.
I'm not betting some anonymous Trumpkin, but will take on somebody serious and real.