Eight justices heard oral arguments in the final case of the Supreme Court’s term on Wednesday. When will the court return to full strength?

That question is as urgent today as it was immediately after the death two and a half months ago of Justice Antonin Scalia. But the initial wave of outrage at the Senate Republicans’ hard-line refusal to consider replacing Justice Scalia has ebbed, making it that much easier for Republicans to keep the seat empty through the presidential election. If they succeed, the court will go nearly two terms, and possibly longer, without a ninth member.

The consequences of the impasse have been growing graver by the day. Already the justices have split 4 to 4 in two cases, leaving important legal issues unresolved. In one, the court failed to decide a major labor case involving the longstanding right of public-sector unions, which represent millions of American workers, to charge collective bargaining fees to nonmembers. By the term’s end in late June, it’s likely that several more cases will have ended in tie votes, including possibly the fights over abortion restrictions in Texas, access to birth control and President Obama’s executive actions on immigration.

It could get worse from here. So far, the justices’ docket for the term beginning in October is smaller than usual, and the eight-member court may hesitate before taking on high-profile cases on controversial topics that are more likely to result in split votes. Already, major cases involving restrictive voting laws in North Carolina and Texas, pharmacists who want the right to refuse to fill contraceptive prescriptions for religious reasons, and Mr. Obama’s efforts to reduce pollution from coal-fired power plants are before the court or could be soon. All could languish in legal limbo.