Both The Washington Post and The New York Times have front-page articles touting Chief Justice John Roberts as the new "swing vote."

From The New York Times, "With Kennedy Gone, Roberts Will Be the Supreme Court’s Swing Vote":

Justice Sandra Day O’Connor became more moderate when Justice William J. Brennan Jr. and Justice Thurgood Marshall left the court, said Michael C. Dorf, a Cornell Law School professor who clerked for Justice Kennedy, and Justice Kennedy likewise moved to the center when Justice O’Connor departed.

“It could manifest in compromise positions in his taking substantively more moderate stances on issues,” Mr. Dorf said. “He might want to go slowly before taking an abortion case or an affirmative action case, or a same-sex marriage case to potentially overturn Justice Kennedy’s handiwork.”...

Mr. Dorf said that Chief Justice Roberts might act differently now that Justice Kennedy — often the deciding vote in those cases — was gone, much like congressional leaders spare their most vulnerable members of Congress from casting deciding votes on politically difficult issues....

“The best hope is to appeal to the chief’s sense of the court as a special, above-politics institution,” [said David S. Cohen, a law professor at Drexel University]. “Overruling [Roe v. Wade or the same-sex marriage case] in these circumstances would make the court and its justices appear like petty politicians.... [But] these justices don’t get to the point they are at in life without being political actors.... and this may be his political goal.”

From The Washington Post, "Roberts gets another key role on Supreme Court: Swing vote" (that's the front-page teaser headline, inside it's "If it wasn’t the Roberts court already, it is the Roberts court now"):

A court in which Kennedy is replaced by another Trump choice “is also likely to encourage conservative legal activists to shoot for the stars — look for cases seeking to overrule Roe v. Wade, reverse or undermine LGBTQ rights, including marriage equality, and erode the progress toward racial justice that the civil rights movement has fought tirelessly to have recognized by an often recalcitrant court,” [said Elizabeth B. Wydra, president of the liberal Constitutional Accountability Center].

Such bold action is not usually Roberts’s style, and the Supreme Court is institutionally averse to overturning precedents, a legal principle called stare decisis. Roberts’s preferred path, his defenders and detractors say, involves limiting the court’s precedents rather than reversing them....

Leah Litman, a liberal law professor at the University of California at Irvine, said the justices need not overturn the same-sex marriage decision to undermine it. “They could recognize a right for religious objectors not to marry LGB individuals; not to serve them; not to provide them health care; not to allow them to adopt,” she wrote.....

Michael McConnell, a former Republican-nominated federal judge and head of the Stanford Constitutional Law Center, said... “If Justice Kennedy is replaced with an interesting, relatively non-doctrinaire conservative (like the best names on Trump’s list) this could augur a more fluid court with a more substantive middle and fewer 5-4 splits,” he wrote in an email.... "Every action seems to have a countervailing reaction,” McConnell said. “It would not surprise me to see a few of the conservative justices breaking more frequently with the liberal side. The court as an institution does not like to see itself as the instrument of an ideological movement.”

ADDED: The center position is so powerful. Having seen the attention and (faux) adulation given to Justice Kennedy over the years, the Justices must be eyeing the vacancy. Some new person will get Kennedy's seat, but he is likely to be a staunch conservative like Gorsuch. The real vacancy we're seeing is in the "swing vote" position, and any Justice could feel pulled to try to sit there. Now, the liberals can't really aspire to occupy the position, but one of them, probably Justice Kagan, might become the force behind the swinging of one of the conservatives, and Roberts is the most likely to get swung. I picture Roberts seeing an opportunity to improve the reputation of the Court and to overcome the overt political look it's acquired over the years. I think there should be more elegant ways to do that than to simply throw his vote to the liberal 4 now and then. But if that's all he can do, I suspect he will.