The new Democratic majority in the House spells big trouble for President Trump, who will now be subject to substantial congressional oversight. But it also could be the first step in unmaking his longer legacy, particularly when it comes to the Supreme Court.

In the past few months, with an eye toward their eventual return to power in Washington, some Democrats have floated the possibility of impeaching Justice Brett Kavanaugh or increasing the size of the Supreme Court. Republicans, in turn, have denounced these calls as illegitimate attacks on judicial independence.

But they are wrong. Tinkering with the size of the court is an extreme measure, to be sure, but such proposals aren’t necessarily an assault on the role of the courts in American government. Rather they are sometimes a response to judges who try to impose their partisan will on a country that has moved in a different direction. Indeed, if the justices want to safeguard their independence, the court must give the elected branches the room to respond to the popular will.

Oversight of the judiciary has been part of presidential and congressional power since the nation’s early years. The election of 1800 produced the first partisan turnover of government control in American history. Thomas Jefferson unseated President John Adams, and Jefferson’s supporters captured both houses of Congress from Adams’s Federalist Party. During the lame-duck session following the election, the Federalists dramatically increased the size of the federal judiciary, and Adams began rushing through the nominations of “midnight judges,” all of whom happened to be loyal Federalists. President-elect Jefferson complained that “the Federalists have retired into the judiciary as a stronghold . . . and from that battery all the works of republicanism are to be beaten down and erased.”

Once the Jeffersonians took control, they impeached Supreme Court Justice Samuel Chase. This maneuver might seem like pure political payback, but the Jeffersonians had good cause for concern. In addition to the Federalists’ blatant court-packing, Chase had launched into partisan rants from the bench, denouncing Jefferson’s supporters in open court during the campaign. The Senate narrowly acquitted Chase, but the episode set a pattern that would be repeated. ...