At the beginning of the 1950s, as White supremacists across the South doubled down on their brutal regime of racial segregation, Thurgood Marshall and other civil rights lawyers from the NAACP Legal Defense Fund found an unlikely ally: the nine White men who then served as the justices of the United States Supreme Court. On May 17, 1954, a unanimous Court declared that “separate is inherently unequal,” overturning thousands of state and local laws that promoted racial segregation in one fell swoop. The Court’s ruling in Brown vs. Board of Education sparked intense popular resistance in the South, resistance that raged over the course of the next half century and even continues to some extent today.

Brown is emblematic of one of the most important functions of the Supreme Court within our constitutional democracy. At its best, the Supreme Court serves as a check on political forces that would otherwise trample on the rights of minorities. Now, the refusal of Senator Grassley and other members of the Senate Judiciary Committee to consider any nominee put forward by President Obama to replace Justice Antonin Scalia threatens the Court’s ability to perform this vital role. A hobbled Supreme Court would not be able to effectively and adequately protect the rights of anyone.

While Brown is the one of the most powerful examples, it is far from the only time in our nation’s history that the Court has stepped in to protect the rights of the African American community against popular majorities. The Court first showed its willingness to do so soon after the adoption of the 14th Amendment when in 1880 it struck down a West Virginia law making it a crime for black men to serve on juries in Strauder v. West Virginia. The Court fully matured into its role as defender of minority rights during the Warren Court era of the 1950s and 60s, during which it issued a series of decisions that systematically dismantled state laws and practices that discriminated against African Americans. Brown itself was a product of that era, as was Loving v. Virginia, the 1967 case that struck down state laws banning interracial marriages. The legacy of the Warren Court era can still be seen in decisions such as 2003’s Grutter v. Bollinger, in which the Court upheld the narrowly tailored use of race in the admissions process by colleges and universities to expand educational opportunity to all Americans.

The Brown decision was unanimous, but landmark cases implicating civil rights in recent years have more often been decided by a one vote margin. Any civil rights attorney today knows that persuading a majority of justices to uphold the interests of minorities can be difficult. Cynics will point out that the Court sometimes gets it wrong when it comes to civil rights issues. But victory is at least theoretically possible when the Court has a full contingent of nine justices.

A vacancy on the Court leaves it with an even number of justices, creating the distinct possibility of equally divided decisions that do not have the force of binding precedent. The importance of having a tie-breaking ninth vote on the Court is underscored by two landmark civil rights decisions issued just last term. In Texas Department of Housing v. Inclusive Communities Project, the Court decided 5-4 that the Fair Housing Act of 1968 allows litigants to bring claims against housing policies that have a racially disparate impact. In Obergefell v. Hodges, the Court—again voting 5-4—struck down same-sex marriage bans across the nation. Every day the Court sits without a tie-breaking vote is a day on which it cannot perform its crucial function to protect the rights of minorities.  Other core cases now pending before the Court concern race conscious admissions policies in higher education, the meaning of “one person, one vote”, restrictions on abortion providers, immigration reform and many other matters impacting African Americans and other people of color.

In 1943, at the height of World War II, Justice Robert H. Jackson encapsulated the Court’s position as the guardian of the Constitution in West Virginia v. Barnette. “The very purpose of a Bill of Rights,” he wrote, “was to withdraw certain subjects from the vicissitudes of political controversy, to place them beyond the reach of majorities and officials and to establish them as legal principles to be applied by the courts. One's right to life, liberty, and property, to free speech, a free press, freedom of worship and assembly, and other fundamental rights may not be submitted to vote; they depend on the outcome of no elections.”

A fully functioning Supreme Court ensures that we do not lose sight of our fundamental constitutional commitments. President Obama will soon identify an able candidate to fill the vacancy on the Court.  And when he does, the Senate Judiciary Committee should abandon its resistance and prepare to swiftly carry out its responsibility of ensuring that the Court has a full contingent of nine justices to carry out its vital role within our constitutional democracy.

Kristen Clarke is President and Executive Director of the national Lawyers’ Committee for Civil Rights Under Law, one of the nation’s oldest civil rights organizations.  Follow her @votingrights.