More than nine months after Justice Antonin Scalia’s sudden passing, his seat on the Supreme Court remains vacant. Instead of allowing President Obama’s nominee, Judge Merrick Garland, to take his place, Senate Republicans, led by Majority Leader Mitch McConnell, have undertaken what the Obama administration is calling “an unprecedented level of obstruction.”

McConnell and his fellow Republicans see Garland’s nomination as an effort by Obama and his supporters to liberalize the Supreme Court. In response, these senators are refusing to hold a confirmation hearing at least until a new president takes office in January. They hope that a President Trump would nominate a more conservative judge in Garland’s place.

In fact, Donald Trump has already presented a list of potential nominees, including federal and state judges. One prominent prospect is Utah Senator Mike Lee, a staunch conservative and close friend of Senator Ted Cruz.

In contrast, Hillary Clinton would have two options if elected – to push Obama’s choice through Congress or to propose her own appointee. Last month on the Tom Joyner radio show, she stated that she would cast a broad net for “common-sense” justices with some “real-world experience.” The worry among conservatives is that Clinton will yield to demands to nominate a younger and more liberal judge: California Supreme Court Justice Goodwin Liu and New Jersey Senator Cory Booker have already been identified as being among those who may be on Clinton’s shortlist.

Although the Senate has the power to refuse to confirm a new justice indefinitely, the strong possibility of a Clinton victory in November means that Senate Republicans should hear the case for Merrick Garland before it is too late to prevent her from filling Scalia’s seat with an appointee further to the left than this reputed moderate. Senate Republicans need to hear the case for Merrick Garland before it is too late. With three justices in their late seventies or early eighties, it is likely that there will be more than one vacancy to fill during the coming presidential term. It is particularly important that the Senate maintain the centrist nature of the court in filling these vacancies. If the vacancies were to be filled by liberal judges, some of the recent high-profile cases that were decided on a 5-4 vote may be overturned, including Burwell v. Hobby Lobby Stores and Wal-Mart Stores, Inc. v. Dukes.

Approving Garland before the next presidential inauguration will both fill the open seat and keep the court from becoming too liberal. If Clinton gets even one vacancy in addition to Scalia’s seat – or if Garland is not confirmed, meaning she can appoint someone in his place – the court is more likely to move strongly to the left. This is even likelier if the Democrats control the Senate after this year’s election, of which there is probably a 50-50 chance. Waiting for the next president, which by all measures could be Hillary Clinton, may end up backfiring on Republicans holding out for the inauguration of Trump.

Until then, Chief Justice Roberts will have to do his best to mitigate the ideological conflict on the court as it tackles cases involving restricted voting rights and gerrymandering in the term that began October 3.