If Donald Trump’s nominee to replace Justice Anthony Kennedy, who announced his retirement on June 27, is confirmed by the Senate, the Supreme Court will have a stable majority of conservative justices for the first time since before the New Deal. Kennedy’s successor will be Trump’s second Surpreme Court pick and may not be his last. Justice Ruth Bader Ginsburg, who is eighty-five, clearly wishes to stay on the Court as long as Trump is president. So does Justice Stephen Breyer, who turns eighty later this year. But neither is immortal. Especially if Trump is reelected, he could potentially replace both of these justices with staunch young conservatives.

The current Court’s four consistent conservatives are all substantially younger than Kennedy, Ginsburg, and Breyer. The oldest, Clarence Thomas, is sixty-nine. Samuel Alito is sixty-eight, Chief Justice John Roberts is sixty-three, and Neil Gorsuch is just fifty. All are self-described constitutional originalists; all favor interpreting statutes based on text rather than their intention; and all have strongly pro-business judicial records. Should Trump appoint a fifth conservative—to say nothing of a sixth or seventh—the conservative majority could easily last a generation.

In light of this prospect, it is not too soon to start asking what a conservative Supreme Court would mean for the country. A conservative jurisprudence, aggressively applied, would reshape American law and politics. It would reinterpret fundamental issues of individual and privacy rights, health care, employment, national security, and the environment. These changes would in turn affect electoral politics. The range of conservative legislation that could survive judicial review would expand, while the range of progressive legislation that could do so would narrow.

In retrospect, it is remarkable that a strong conservative majority on the Court has not emerged before now. Since 1980, Republicans have held the presidency for twenty-two years and Democrats for sixteen. Ronald Reagan, who campaigned on the platform of choosing conservative judges, appointed three justices—Antonin Scalia, Sandra Day O’Connor, and Kennedy—and elevated William Rehnquist to the chief justiceship. That should have established conservative control. Yet O’Connor turned out to be a centrist, controlling the Court for a quarter-century by casting the decisive fifth vote in controversial cases. When she retired in 2006, Kennedy assumed her position as the swing justice and unexpectedly emerged as a liberal hero, voting, for example, to extend constitutional rights to detainees in Guantánamo Bay and marriage rights to same-sex couples.1

George H.W. Bush also had the chance to consolidate a conservative majority. He appointed Thomas to replace Thurgood Marshall but also replaced William Brennan with David Souter, who underwent a subtle yet significant evolution from Burkean conservative to Burkean liberal. Bill Clinton, George W. Bush, and Barack Obama each got two justices confirmed, which maintained the Court’s balance. That conservative control has been so long in coming reflects either miscalculation by Reagan and George H.W.…