A delicate balance on the U.S. Supreme Court was blown up Wednesday by the announced retirement of Justice Anthony Kennedy.

Although he was a Reagan appointee and a conservative on most issues, Kennedy nonetheless cast key deciding votes that protected socially liberal values, such as a woman’s right to choose an abortion and the ability of same-sex couples to marry.

Now President Trump is preparing to nominate a successor who would push the court more reliably rightward, not just during Trump’s time in office but possibly for decades.

And thanks to a narrow one-vote Republican majority in the U.S. Senate, there are very few people who can stand in his way. One of them is Maine Republican Sen. Susan Collins.

Collins could have a lot to say about this nomination if she chooses to weigh in.

ALL REPUBLICANS NEEDED

Trump and Senate Majority Leader Mitch McConnell of Kentucky would need almost every Republican vote to force through an appointment in the face of Democratic opposition. If only two Republicans refused to be rushed, the nomination could not go forward.

Collins can and should demand that any replacement for Kennedy reflect the retiring justice’s unique position on the court over the last three decades. Collins can and should require that Kennedy’s replacement have bipartisan support and should not be confirmed by a 50-to-49 vote by the current Senate.

A nomination this consequential demands less deference to the president than Collins usually demonstrates. There are thousands of Americans who have the kinds of resumes that would qualify them to serve on the court, but what this nominee believes matters as much as their credentials.

The court’s conservative majority showed this week, with a decision that undid more than 70 years of labor law, that there is no consensus on what it means to respect precedent or what constitutes judicial activism. Until we arrive in an era of common understanding, the best we can hope for is balance.

And the loss of Kennedy could mean the loss of balance. For instance, it would take only one vote on the Supreme Court to overturn Roe v. Wade and send abortion law back to the states, ending nearly a half-century of constitutional protection.

PROCESS POLITICIZED

Supreme Court nominations have become increasingly politicized since the failed Robert Bork nomination in 1987, which led to Kennedy’s appointment.

In 2016, Republicans took the unprecedented step of refusing as much as a hearing to President Barack Obama’s nominee, Judge Merrick Garland, keeping the seat open until after the election.

Democrats responded by filibustering Trump’s nominee Neil Gorsuch, and the Republicans came back with the “nuclear option” of changing the Senate rules to require no more than a majority vote to confirm a Supreme Court justice.

Collins voted for the rule change, but said she did so with regret. She said the Senate would need to restore “the unwritten ethos that has made this body a model for the world for 230 years. It is an ethos built upon trust, compromise, and restraint.”

Those three qualities should be on Sen. Collins’ mind again as this process moves forward. Balance on the court is worth maintaining in these divided times.