The prospect of Brett Kavanaugh on the US Supreme Court is, for abortion rights advocates, the nightmare scenario: the entrenchment of a fifth vote to overrule Roe v. Wade and open the door to banning abortion in much of the country. As Democratic leaders and abortion rights groups go to the mattresses to defeat Kavanaugh, they are cranking up the apocalyptic rhetoric. “Our right to make the most fundamental decisions about our bodies, our families, and our lives has been all but eradicated,” bewails the president of NARAL. “Kavanaugh would use the Court as a tool to doom all women to that fate.”

Anything is possible. But when Americans are asked if they want to see Roe overturned, two-thirds of them consistently say the 1973 landmark should stand. If history is any guide, the Supreme Court will not ignore such strong public sentiment. The last time it had an ideal opportunity to strike down Roe, in the 1992 case of Planned Parenthood v. Casey, a majority of justices recoiled. Justices Anthony Kennedy, Sandra Day O'Connor, and David Souter — Republican appointees all — wrote an opinion saying that to backtrack on Roe would cause “profound and unnecessary damage to the court’s legitimacy,” and that it was “therefore imperative to adhere to the essence of Roe’s original decision.”

Yet if Roe were to be overturned, would it really be the calamity that Democrats anticipate with such horror?

Roe v. Wade was a terrible decision. Even staunch defenders of abortion rights have long conceded that Justice Harry Blackmun’s opinion was intellectually and legally incoherent. As a matter of constitutional reasoning, Blackmun’s own former law clerk, the prominent (and pro-choice) lawyer Edward Lazarus, has written, “Roe borders on the indefensible.”

At least as bad as Roe‘s legal flaws is what it did to U.S. politics. It turned abortion into the most bitterly contentious issue in American life. By yanking abortion policy from the states and abruptly legalizing it everywhere, Roe contributed powerfully to the polarization of the two major parties. In Roe’s wake, both moved to the extremes. The Democratic Party embraced no-exceptions support of abortion, fighting even mild restrictions most voters support. The GOP became uncompromisingly antiabortion, opposing all subsidies for abortion and supporting a constitutional amendment to protect life in the womb from conception.

But while Roe’s permissive abortion rules today are defended unswervingly by Democratic officials, it is the Republican Party that reaped by far the greater political gains from what the Supreme Court did.

Wooed by GOP leaders beginning with Gerald Ford, tens of millions of antiabortion voters, many of them evangelical Christians, moved into the Republican camp. As Democrats grew increasingly adamant in defense of legal abortion, and as Republicans ever more vehemently called for Roe to be toppled, religious conservatives abandoned the Democratic Party. In the interest of halting what they devoutly regard as a moral obscenity — the destruction of more than 60 million unborn babies since Roe was decided — right-to-life voters have been willing to support even deeply flawed Republican candidates, as long as they promise to work to overturn Roe.

With antipathy to Roe as a source of solidarity, the GOP has triumphed at the ballot box. President Trump underscored the point in a speech to the Susan B. Anthony List in May. “For the first time since Roe v. Wade,” he exulted, “America has a pro-life president, a pro-life vice president, a pro-life House of Representatives, and 25 pro-life Republican state capitols. That is pretty good.”

But what becomes of that solidarity if Roe v. Wade is overruled? Once the great goal that animated them for so long is achieved, how many of those single-issue voters will still feel obliged to support Republicans no matter what?

Come to think of it, how many of those voters will keep seeing Republicans as reliably antiabortion?

Remember, the end of Roe wouldn’t mean the end of abortion rights — it would mean that abortion policy would be crafted in Congress and the state legislatures. Suddenly, Republican lawmakers would find their antiabortion principles put to the test. For decades, they have been able to call for rigidly restricting abortion or banning it outright, knowing that, under Roe, such calls would remain purely theoretical. But in a post-Roe world, Republican legislators would lose that easy out. Go too far in cracking down on abortion, and they would face the wrath of pro-choice voters who want abortion rights preserved. Fail to go far enough, and they would face the wrath of evangelical voters who expected, at long last, to see abortion shut down.

The Republican Party that for 40 years has clamored for a Supreme Court majority to scrap Roe, writes law professor Jonathan Turley, is like the proverbial dog chasing cars: What happens if it gets what it wants?

Reversing Roe would throw Republicans into put-up-or-shut-up territory that many of them would be unable to navigate. But for Democrats, the demise of Roe would be liberating. No longer would they be compelled to defend the most outrageous abortions, like those on healthy fetuses of the “wrong” sex. They would be free instead to support reasonable restrictions on abortion, as most Americans do.

The abortion debate has been so shrill for so long because the Supreme Court prevented Americans from working out the issue for themselves. The thought of overturning Roe fills Democrats with alarm, but it shouldn’t. Return abortion to the democratic arena, and Democrats might be surprised at how much they stand to gain.

Jeff Jacoby is a columnist for The Boston Globe.