The GOP has been trying to repeal the ACA ever since it became the law of the land. So far, they have failed to do so. It would be political suicide if they managed to repeal it without immediately replacing it with their own plan. Do they have one? No. But why not? They have had more than six years to come up with one. The only reason they want to repeal the ACA isn’t merely because the cost of premiums going up, they were much lower when the ACA first started, and they wanted to repeal it then. I think the only reason they are so hellbent on repealing it is because President Obama accomplished something that they couldn’t, and that is what really irks them about it.
So, why does the GOP insist on repealing the ACA and throwing 22 million people off of their healthcare insurance? For many, this is the first chance they had to actually get health insurance, due to pre-existing illnesses. And for those who could not afford it, the ACA offered subsidies to those people. Why can’t the GOP keep the ACA in place and… here’s a thought... FIX IT! Figure out a way to lower premiums, discard the parts of it they don’t agree with, but make sure that it is available to everyone who needs it, wants it, or already has it, including those with pre-existing conditions, and children - for any reason. This way, those who are covered by the ACA will not have to lose it.
If the GOP doesn’t like the ACA simple because it is credited to Obama, change the name, fix it, and call it their own. Trump takes credit for fixing everything (even if he didn’t fix it), so he would be more than happy to sign a healthcare bill with his name attached to it in some way.