Here's why:
If you take a look at the LA Times article, there is this interesting perpsective that will worry the GOP a lot more than the Democrats.
It may sound harsh, but if Roe v. Wade is overturned, then we going to see huge losses in the GOP column. Why? Because many people do not want this decision to be overturned. Look at the issue. Polls state that an overwhelmingly majority do not Roe v. Wade to be overturned. Furthermore, it cause the GOP to split into two fractions: the theocrats and the moderates. The moderates are the ones that the GOP needs to be concerned. Because if the GOP further transforms itself to a theocratic party, then they will leave the GOP and go into a third party affiliation. That will leave open the possiblity of the Democrats having a bigger majority if this decision is overturned.