Trump signed an order expanding short term coverage, but both red and blue states are pushing back due to the projected effects of expanding short term coverage on the broader marketplace.
In simple terms, short term plans are low cost / low benefit plans that don’t have to follow the ACA’s rules and can thus end up being cheaper for some healthy people.
Short term plans used to be limited to… a short term… but in an effort to repeal and replace the ACA through the executive (since a repeal and replace couldn’t get through Congress), Trump signed an order expanding these plans.
This would likely help some families get cheaper coverage, but for other families, employees, and tax payers it would likely mean paying more (as the theory is that costs would get pushed into different markets which no longer had the healthy customers bringing down the price for everyone by decreasing the overall risk an insurer was taking on).
Due to those concerns, many states are in practice rejecting the new short term plan rules despite HHS urging states to corporate with the Federal Government.
That is the gist, I personally like Charles Gaba’s take on the issue of short term coverage, check that out for more detail.