Roberts is likely to be key in the 2020 cases involving Trump as well. Many have said that he cares greatly about the court’s credibility. The hope is that he will realize that ruling in favor of the Trump administration in these cases would not only fly in the face of established precedent; it would also make the court seem highly partisan and strike a serious blow to its institutional legitimacy. But Roberts is deeply conservative, and the critical question for 2020 will be whether he — or any of the conservative justices — can put partisanship aside and say no to Trump.