UPDATE: David Kurtz ponders the implications:
On one level it's surprising anytime the Supreme Court takes up any one case simply because they don't step in very often, especially in election cases (with notorious exceptions), especially on an issue that has not been previously heavily litigated. But it's less surprising how the court came down here.
It didn't address the merits of the case per se (although in some ways the court's ruling goes straight to the merits). Rather, it found that the GOP was unlikely to prevail on the issue of whether the Help America Vote Act (the law at issue here) allows private citizens or groups to sue to enforce the law. If the law doesn't create a so-called private right of action, the GOP has no standing to sue in the first place. Likelihood of prevailing on the merits is a key criteria for taking the extraordinary step of granting a TRO. Since the justices thought the GOP would ultimately lose on that argument, they vacated the TRO.
Now, I'll be curious to see where the GOP goes from here. There's not enough time to pursue this case on the merits before the election. So as a practical matter it may kill the case in Ohio entirely. But perhaps more importantly, it puts a stop to the GOP or any other private party gumming up the works over the next 18 days by filing similar cases in courts across the country.