This time the Democrats are not running on Obamacare per se. They’re running on pre-existing coverage and while Obamacare as a whole may not be universally popular the pre-existing coverage part of it is. If their lawsuit manages to strike down Obamacare as unconstitutional then the pre-existing requirement is gone with it. The GOP has nothing to replace it with. And healthcare consistently polls at or near the top of voter concerns.
One of the reasons that Obamacare was an unmitigated failure was how they implemented pre existing conditions. Under Obamacare, you could buy your medical insurance when you needed it, as they were wheeling you into the ER on a gurney. This drove the price of health insurance through the roof. In order to offer no pre existing conditions, you have to spread the risk to everyone and everyone has to carry coverage as you must do with automobile insurance.