SOMEWHERE ON US-218 BETWEEN MOUNT PLEASANT AND KEOKUK, Iowa — New Jersey Sen. Cory Booker, a candidate for the 2020 Democratic presidential nomination, said in a interview with HuffPost that he’s open to proposals to reform a Supreme Court dominated by conservatives, but thinks adding more seats to the court will only result in an unproductive arms race with Republicans.

Democrats are debating whether they should add seats to the Supreme Court in an effort to create a liberal majority among the justices after the infamous GOP blockade of President Barack Obama’s nomination of Merrick Garland in 2016 and the contested confirmation of Justice Brett Kavanaugh in 2018. Booker, who is typically cautious on procedural matters, said the party should look at other ways to change the court and hopes it can be a “moderating” force in American politics.

“I am open to us finding a way to stop the extremist tilt of the Supreme Court, and I’ve seen a number of different models and possibilities about how to reorganize the Supreme Court, from term limits to rotating people on the court,” Booker said in an interview aboard his campaign RV in Iowa. “I’m open to everything.”

But Booker said he also doesn’t want to create a “race to the bottom” between the two major American political parties.

“If Democrats add people when we have an alignment of power, and that’s the totality of our reforms, then it’s clear that Republicans are going to try to do that as well,” he said. “And one day our grandchildren will ask us: ‘Hey, Granddad, why are there 121 people on the Supreme Court?’”

“We should be very thoughtful about this and try to bring back that kind of moderating force the judiciary has always had,” he said.

Sen. Bernie Sanders (I-Vt.), another contender for the 2020 Democratic nomination, has staked out a similar position. South Bend, Indiana, Mayor Pete Buttigieg has suggested increasing the size of the court to 15 justices, but also requiring at least five of the justices to have the approval of the first 10. Sen. Kamala Harris (D-Calif.) has said she’s “open” to adding more seats to the court.

While there is a long-standing precedent of placing nine justices on the Supreme Court, the actual number is not laid out in the Constitution. Some Democrats have begun to argue the Republican blockade of Garland’s nomination amounted to the GOP changing the number of justices on the court unilaterally for a year.