U.S. Sen. Marco Rubio has introduced a constitutional amendment that would limit the Supreme Court of the United States to nine justices.

He has the support of a number of fellow GOP senators, including Mitt Romney of Utah.

Rubio’s move is in response to Democratic proposals to expand the high court.

“The Democrats’ court-packing proposal represents the latest shortsighted effort to undermine America’s confidence in our institutions and our democracy. America’s institutions are far from perfect. But over the past two centuries, they have provided a framework for our nation to become the most dynamic, most vibrant, and most exceptional nation in all of human history,” Rubio said. “To prevent the delegitimizing of the Supreme Court, I am introducing a constitutional amendment to keep the number of seats at nine. Our institutions matter. Our Constitution matters. And we should fight to protect them.”

The Supreme Court has had nine seats since 1869.

“Society is only as strong as its institutions, and we should resist any effort to treat the Supreme Court like one of the elected branches. Recent court-packing proposals are transparent attempts to rig the Court based on political preferences. This constitutional amendment would ensure the integrity and independence of the Supreme Court for generations to come,” said Romney.