"The decision merely says that 'state courts do not have free rein' and that they may not 'transgress the ordinary bounds of judicial review...'"

"'... such that they arrogate to themselves the power vested in state legislatures to regulate federal elections.' The court offers no concrete understanding nor any example of what that means. It’s clear that a majority was cobbled together among conservative and liberal justices by agreeing to decide this part of the case in the narrowest terms.... [T]he state court interpreted general provisions in the state constitution — such as that requiring elections to be 'free and fair' — to in effect ban partisan gerrymandering. Whether this decision transgresses ordinary judicial review or exemplifies it remains a mystery. Had the court resolved that question, it would have provided much-needed guidance for 2024.... Judicial minimalism can be a virtue in many contexts.... But in the context of election law, it can be a vice. Elections benefit greatly from clear rules laid out well in advance of Election Day.... Clear rules specified in advance are all the more important in this era of pervasive distrust and suspicion concerning elections...."

Writes lawprof Richard H. Pildes in "The Supreme Court Rejected a Dangerous Elections Theory. But It’s Not All Good News" (NYT).

The love for clear rules is easier to express after the Court has rejected the clear rule your opponents were pushing. 

ADDED: Pildes declines to mention Bush v. Gore, but that's the precedent here. From the majority opinion in yesterday's case, Moore v. Harper:

Members of this Court last discussed the outer bounds of state court review in the present context in Bush v. Gore, 531 U. S. 98 (2000) (per curiam). Our decision in that case turned on an application of the Equal Protection Clause of the Fourteenth Amendment. Id., at 104–105. In separate writings, several Justices addressed whether Florida’s Supreme Court, in construing provisions of Florida statutory law, exceeded the bounds of ordinary judicial review to an extent that its interpretation violated the Electors Clause. 

Chief Justice Rehnquist, joined in a concurring opinion by JUSTICE THOMAS and Justice Scalia, acknowledged the usual deference we afford state court interpretations of state law, but noted “areas in which the Constitution requires this Court to undertake an independent, if still deferential, analysis of state law.” Id., at 114. He declined to give effect to interpretations of Florida election laws by the Florida Supreme Court that “impermissibly distorted them beyond what a fair reading required.” Id., at 115. Justice Souter, for his part, considered whether a state court interpretation “transcends the limits of reasonable statutory in- terpretation to the point of supplanting the statute enacted by the ‘legislature’ within the meaning of Article II.” Id., at 133 (Souter, J., joined by Stevens, Ginsburg, and Breyer, JJ., dissenting). 

We do not adopt these or any other test by which we can measure state court interpretations of state law in cases implicating the Elections Clause. The questions presented in this area are complex and context specific. We hold only that state courts may not transgress the ordinary bounds of judicial review such that they arrogate to themselves the power vested in state legislatures to regulate federal elections.

The new opinion creates pressure on state courts to resist going too far as they follow their own political preferences under the guise of applying the law. Deciding based on politics is something they shouldn't do at all, but they are human and willful, and everyone knows it's impossible to eradicate the pull of these preferences. What we've learned is that there's a limit, and the Supreme Court won't tell us exactly what it is. The state courts can internalize restraint or they can lean toward activism and find out.

ALSO: Consider the unclarity in Pildes's expression of love for clear rules:

For illustrative purposes, let’s say in 2024 the Wisconsin state legislature passes a law establishing deadlines for requesting or returning absentee ballots, but a state court rules those deadlines unconstitutional because they contradict the state constitution’s guarantee of the right to vote. The losing party will now turn to the federal courts and argue that the state court has gone “too far” in its interpretation of the state constitution.

The clearest clear rule in that hypothetical is the legislature's specification of deadlines. The state court injects unclarity — and seems to display political will — by seizing upon the vague concept of "the right to vote" and using that to overcome the clear deadlines. The federal court, asking whether that goes "too far," would in fact defending us the people of Wisconsin from the activism of a politicized state court.