The Republican presidential hopefuls have been saying alarming things about the federal courts.

Newt Gingrich and Rick Santorum want to abolish the United States Court of Appeals for the Ninth Circuit, which Mr. Gingrich says is “consistently radical” — meaning it upholds civil rights and civil liberties and other things he doesn’t like. Michele Bachmann and Ron Paul say they would forbid the Supreme Court from ruling on same-sex marriage, forgetting perhaps that presidents don’t actually get to do that. Rick Perry has called for term limits for Supreme Court judges, although he hasn’t said whether he meant all of them, or just the liberal ones.

And that is as close as any of the Republicans have come to confronting the real significance of the federal courts in this election — the makeup of the Supreme Court. When Chief Justice John Roberts Jr. began the new Supreme Court term by congratulating Antonin Scalia on his 25th anniversary as a justice, it was a reminder that Justice Scalia is now 75 as is Anthony Kennedy and that Ruth Bader Ginsburg is 78.

Since 80 is the average retirement age of justices over the past generation, whoever is elected president could shape the court for the next generation. That means voters should be alarmed by the fringe ideas they have been hearing from the Republican candidates so far.

The Roberts court is closely divided but also the most conservative since the 1950s. Four of the nine members are very conservative, three of them under 64. If the president is a Republican and has the chance to fill Justice Ginsburg’s seat, that could turn the court decidedly conservative for decades. If President Obama is re-elected and has the chance to fill Justice Scalia’s seat, that could turn the court into a more moderate one.