Democrats running for president might want to tread carefully before taking stands likely to hurt them and their party in 2020, including Medicare for All and taking guns away from people by voluntary or compulsory buybacks. Trump is already using Beto O’Rourke’s support for the latter as an excuse to do nothing on gun control.

Now we can add another one—packing the Supreme Court by expanding the number of justices. Their thinking is that when they win the White House, they will be able to appoint enough Supreme Court justices and federal court judges capable of reversing the conservative decisions they oppose, and who will deem constitutional the laws they pass through Congress.

New York Times columnist Jamelle Bouie tried to make a case for it, disingenuously arguing that he was supporting packing the court not “to make the courts a vehicle for progressive policy, but to make sure elected majorities can govern—to keep the United States a democratic republic and not a judge-ocracy.”

Time magazine thinks “it’s the next big idea in the Democratic primary,” and that may be right. Some Democratic activists have already created a “Pack the Courts” group lobbying Democrats to endorse the proposal. Brian Fallon, a Democratic strategist, told Time that what he calls “the Kavanaugh Court” is nothing but a “partisan operation,” and that without court-packing, democracy can no longer function.

When The Washington Post asked the Democratic candidates whether they favored packing the Supreme Court, Corey Booker answered, “I’m taking nothing off the table.” Pete Buttigieg told the paper he is open to packing the court and wants “structural reform” with more than simply adding judges; Kamala Harris says citizens are on “the verge of a crisis of confidence in the Supreme Court,” and hence “everything is on the table”; Jay Inslee (no longer in the race) says it was Mitch McConnell who destroyed Americans’ faith in the court, “by stealing a seat from Barack Obama” and would consider “any ideas… on how to reset that balance.”

Before moving in that direction, Democrats should study what happened after Franklin Roosevelt proposed court-packing in February of 1937, after the court ruled that two bills that had passed Congress, the National Recovery Act (NRA) and the Agricultural Adjustment Administration (AAA), were unconstitutional. Already the court had ruled that a New York state minimum wage bill was unconstitutional, as was a proposed act for conservation of coal.

Democrats were concerned that the proposed Wagner National Labor Relations Act, which would institute collective bargaining, would be the next to go down to defeat, as well as fearing that bills already passed by Congress, such as the Social Security Act, would meet with the same fate.

The president publicly called for measures to “revitalize the court.” He questioned whether elderly judges who were infirm should be sitting on cases and proposed that he have the right to appoint a new judge if a federal judge who had sat on the bench for more than 10 years was still serving six months after he reached the age of 70. That, he thought, would allow him to appoint six new judges to the Supreme Court, and 44 to the lower federal courts. The ruse didn’t work. Some of his most progressive justices were in their seventies and eighties and were completely competent. These septuagenarian and octogenarian justices, federal judges, and senators were furious, and resented the Supreme Court justices being referred to as “nine old men.”

The response to FDR’s call was outrage from both sides of the aisle, as well as from the American public. The president was stunned to find that in the Senate, opposition came not only from Republicans and conservatives, but from senators who previously had supported everything Roosevelt had called for. Principled liberals also did not warm up to the proposal, even though they hoped along with Roosevelt that reforms put on hold would pass and become law.

Oswald Garrison Villard, editor of the progressive weekly The Nation, wrote a journalist friend that Woodrow Wilson had brought segregation into the federal government, and that a future Wilson “could pack the Supreme Court so that no Negro could get within a thousand miles of justice.” The editor and progressive William Allen White feared that a “reactionary president” could use this power to change the court in a bad direction and might even try to “abridge the Bill of Rights” via emergency legislation that the court would then approve.

The court may not have been approving FDR’s earlier programs, but most citizens believed in the separation of powers and the role of the Supreme Court in judging the constitutionality of proposed laws passed by Congress. The New Deal historian William Leuchtenburg wrote that the president “had attacked one of the symbols which many believed the nation needed for its sense of unity as a body politic.”

FDR would later famously say that he lost the battle for court-packing but had won the war. At the end of March, the court actually upheld the minimum wage law, and shortly after, found the Wagner Act constitutional. Finally, in May, the court ruled in two different 5-4 decisions that unemployment insurance in the Social Security Act and old-age pensions were both constitutional.

Yet, FDR was not satisfied by the change in the justices’ reading of the law and persisted with his goal of Court packing. A group of reliably pro-New Deal Senators continued to attack him, arguing that even if court-packing was instituted, new justices would be as likely as those already sitting to rule against laws the president favored. They respected the court’s role, respected the separation of powers, and believed Roosevelt’s path endangered the very basis of the constitutional government. Moreover, the public outcry against FDR’s plan made it clear that the Supreme Court was an institution that the country respected.

FDR continued his effort even after a justice announced he was retiring and he was sure he could get 6-3 justices voting in favor of forthcoming legislation, only to finally give up in mid-July, when the last Democratic senator supporting him on the issue suddenly died. In the next few years FDR was able to appoint five liberal justices to the court. Yet, as Leuchtenburg concludes, “the Court fracas destroyed the unity of the Democratic Party and greatly strengthened the bipartisan anti-New Deal coalition.”

Today, with some Democrats raising the specter that if they win the White House they would forcibly take away people’s guns and deprive them of medical insurance they already have, and with Trump and his acolytes arguing that a Democratic victory would move toward making America a socialist country, it is pure folly to give the GOP more ammunition by adding court-packing to their docket. That is the charge Donald Trump will make against whatever candidate wins the Democratic primaries. Democrats must ask: Do you really want to hand Trump another bludgeon to use in the 2020 campaign?