Not substantial, but there will definitely be an effect on Senate races in particular, or even in driving up turnout of female voters. Most of the time though, it seems like less voters than thought seem to vote based on the Supreme Court. That's assuming that they even care or understand it.
Yes, I think voter motivation based on SCOTUS is very overstated, as shown by some 2016 exit polls. If voters were presented with a list of issues that were most important to them, with SCOTUS on the list, it was a factor for something like 20% of voters (I'm doing this from memory so these numbers may be a bit off.) But when asked an open-ended question about what issues motivated them, only about 2% of voters mentioned the Court.
Poll
