a little bit

Casey changed the calculus in Roe a little bit. There still is a fundamental right to an abortion. That's the 'central holding.'

But casey rejected the trimester system set up in Roe. Roe said that you could have all the abortions you wanted up until the 2nd trimester, at which point the state could put more restrictions.

Casey says viability instead of 2nd trimester. So, it's a little more flexible, but it's also under attack. That's why you see billboards with things like, "I got my GENES at conception," or "A baby's heart start's beating at 8 weeks." (or whatever). The entire point of those billboards is to push forward the idea of when a fetus becomes viable.

The second thing Casey did was say that the state couldn't 'unduly burden' the right to an abortion before viability. So, in Casey, the spousal notification requirement was thrown out because it effectively gave a veto to the husband/father of the child that would have been impermissible if the state had exercised that same power.

I think Roe/Casey could be refined, but that's not what I'm talking about. My point is that a right wing Court will create the conditions necessary to undermine the precedent bias that sustains Roe and Casey.