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Who Would Win a Battle Between a Liberal Congress and a Conservative Supreme Court?

Research suggests threats from Capitol Hill can make key justices skittish about overturning popular legislation.
Morning light shines outside the U.S. Supreme Court building on March 20th, 2017, in Washington, D.C.

Morning light shines outside the U.S. Supreme Court building on March 20th, 2017, in Washington, D.C.

Whatever happens with Brett Kavanaugh, the Supreme Court will in all likelihood soon be shifting to the right. President Donald Trump's next appointment to the body, be it Kavanaugh or someone else, will be ideologically predisposed to rule in ways that favor the conservative cause.

Liberals envision a nightmare scenario in which progressive legislation passed by a future Democratic Congress and signed by a Democratic president is consistently vetoed as unconstitutional. They fear entrenched interests will use this power to prevent progress on everything from climate change legislation to universal health care.

Such a battle between branches of the government could further weaken our democracy, as angry voters come to see the court as illegitimate. But this sort of dispute is not new. Over the decades, a challenged Congress has periodically engaged in "court-curbing"—that is, considering legislation that would restrict the power of the judiciary.

Seminal research from a decade ago reveals this can be an effective counterweight against a Supreme Court that defies public opinion. And a second, just-published study explains why.

It finds two justices are particularly sensitive to the implied "watch yourself" message of such legislation: the chief justice, and the swing justice whose vote tends to decide contentious cases.

"Court-curbing is an effective tool for Congress," political scientists Alyx Mark and Michael Zilis write in the Political Research Quarterly. They report that, historically, the judiciary is less inclined to overturn legislation on constitutional grounds "when faced with formal threats from the legislature."

Evidence of this dynamic was presented by Emory University political scientist Tom Clark in his 2009 study. He created a database of court-curbing bills introduced in Congress between 1877 and 2006, and analyzed how such proposals influenced subsequent Supreme Court decisions.

"An increase in the level of court-curbing in one year is associated with a decrease in the number of laws held unconstitutional the following year," he reports. "Court curbing has deterred between 10 and 20 constitutional invalidations each decade—as many as two per year in some instances."

Clark continues: "Given that only about two laws are held unconstitutional each year ... this finding is indeed substantial." He adds that "the constraining effect of court-curbing increases as the Court becomes more pessimistic about its public support."

Mark and Zilis' new paper refines those results by examining precisely which justices are more likely to be swayed by such signs of congressional disapproval.

"Court curbing is particularly impactful in shaping the behavior of the chief justice, whose administrative duties require regular interactions with Congress, and the swing justice, who as an ideological moderate is attentive to a variety of external signals, including threats from the legislature and opposition from the public," they write.

They found those two justices have, traditionally, been "much less likely to strike down federal legislation" than their colleagues.

With the retirement of Anthony Kennedy, Chief Justice John Roberts will essentially play both of those roles. Although a conservative, he's as close to a swing vote as the new court is likely to have, and he is highly invested in maintaining the institution's legitimacy in the eyes of the public.

If the past is any guide, that suggests he will be reluctant to overturn popular legislation—especially if the court's image has already been tarnished by the seating of a second accused sexual offender.

Of course, these are highly polarized times, which could change his calculus. The Democrats are, at best, two years away from control of the federal government. And if Trump gets yet another Supreme Court appointment, all bets are off.

Nevertheless, this research suggests that, if Kavanaugh makes it to the court, his unique unpopularity decreases the likelihood a five-vote majority will reflexively invalidate liberal-leaning laws.