Ronald A. Klain served as a senior White House aide to Presidents Barack Obama and Bill Clinton and is an adviser to Joe Biden’s 2020 presidential campaign.

At last week’s Democratic presidential debate, two issues — abortion and the Supreme Court — finally made it onto the agenda. But the relatively abstract discussion of potential schemes to add to the court’s membership or rotate justices off the court masked a critical point: Circumstances may be conspiring to put abortion and the court at the center of 2020’s campaign in a way unmatched in a generation.

Why? Because of the potential convergence of two gigantic events in June 2020. First, that is when the Supreme Court is expected to hand down a decision in a Louisiana abortion case — a ruling that will likely substantially restrict abortion rights even if it does not outright overturn Roe v. Wade. Second, notwithstanding his public protestations to the contrary, Justice Clarence Thomas may retire that same month, setting off a brutal battle over his replacement.

Either of these, taken alone, would be enormously significant. Together — and in the midst of a presidential campaign — they would be cataclysmic.

Conservative activists are not being shy in urging the court to use the Louisiana case to overturn Roe. Even if the court does not go that far, it is likely to give state legislatures expanded powers to restrict access to abortion, allowing states to effectively “regulate abortion clinics out of existence.” The Louisiana law at issue is almost identical to one rejected by the court in 2016, when then-Justice Anthony M. Kennedy cast the deciding vote. A decision by the court to overturn that ruling would provide a clear signal of a new direction under a new conservative majority.

And what if, at almost the same moment, Thomas, the court’s senior justice, steps down? That move would set off an unprecedented effort to secure a confirmation vote on a Supreme Court vacancy after Labor Day in a presidential election year. Although Thomas in June dismissed “this rumor that I was retiring,” if Trump is trailing in the polls next summer, Thomas could face pressure from GOP insiders to give Trump a shot at filling his seat to avoid any risk of handing it over to a Democratic president to fill.

While Justice Ruth Bader Ginsburg — older than Thomas — eschewed similar considerations in declining to retire during President Barack Obama’s tenure, Ginsburg has always been more distant from the Democratic Party than Thomas is from the GOP. Thomas was a political appointee in the Reagan administration. His wife, Ginni, is a conservative activist with close ties to key GOP figures; she has lobbied the Trump White House on conservative legal issues. These ties could put pressure on Thomas to step down, or another justice, perhaps conservative Samuel A. Alito Jr., could choose to leave.

How would this impact the 2020 race? In recent times, the Supreme Court has been an electoral issue that has favored the Republicans. In 2016, Trump won voters who rated the Supreme Court as their No. 1 issue by a 60-40 margin. In 2018, the controversy over the Brett M. Kavanaugh nomination probably helped Republicans expand their majority in the Senate. Republicans might believe that a Supreme Court confirmation battle could work to their political advantage.

But things may be different in 2020.

History provides a guide. In late June 1992, Bill Clinton was in third place in the general election contest, trailing George H.W. Bush and independent Ross Perot. Then, the Supreme Court handed down a decision in Planned Parenthood v. Casey, which stopped short of overruling Roe but cut back on constitutional protections for abortion rights. Both sides then “rushed to declare defeat,” warning voters that the next election would decide the future of the court’s abortion decisions. The Clinton campaign put abortion rights and the Supreme Court front and center.

Just 30 days later — in part fueled by a galvanizing of pro-choice suburban support behind Clinton — Clinton took a lead in the race and never looked back. Less than a year later, Clinton named Ginsburg to replace longtime Roe opponent Byron White.

Pro-choice advocates and Democratic senators need to work together to lay the groundwork for the kind of public opinion explosion that followed the Casey decision in 1992. They should be quietly approaching the swing votes in the Senate — Democrats and Republicans — seeking commitments to oppose action on any Supreme Court nomination late in the election year; if Merrick Garland’s nomination was too late in March 2016, a pick in late June clearly should be out of bounds. And they should emphasize the enormous risk of giving Trump four more years — and more Supreme Court picks: If that were to happen, the court would not only reverse Roe and allow states to ban abortion; it might adopt a federal constitutional rule limiting abortions nationwide.

Republicans and the legal right — who are anticipating a favorable ruling in the Louisiana case and may get tipped off about any court retirement plans — will be ready. Will Democrats and the legal left be as prepared?

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