By Richard Wolf

Before the first votes were cast for president in last year’s primaries and caucuses, Donald Trump picked a fight with John Roberts.

“Justice Roberts turned out to be an absolute disaster,” Trump said a year ago, dropping the title of chief justice that makes Roberts first among equals on the Supreme Court. “He turned out to be an absolute disaster, because he gave us Obamacare.”

Shortly after noon Friday,  the 17th chief justice of the United States will deliver the oath of office to the 45th president of the United States. It could be the start of a match made in heaven — or the high point of a rocky relationship.

If Trump gets to replace more than one justice during his presidency, it would cement the court’s conservative majority and Roberts’ place at its helm, an Election Day gift that could have been coal if Hillary Clinton had won the White House.

If, on the other hand, potential policy forays such as a ban on Muslim immigration or ethics entanglements involving Trump’s real estate empire prompt constitutional challenges, Roberts’ court could become the final arbiter of Trump’s fate.

“He is unlikely to look favorably upon actions of the Trump administration that might really run afoul of well-established principles of our Constitution and the way our government normally operates,” says Brianne Gorod, chief counsel at the liberal Constitutional Accountability Center, who led a 10-year review of Roberts’ record last year. While Trump has vowed to nominate a doctrinaire conservative in the next few weeks to replace the late Justice Antonin Scalia, Roberts’ brand of conservatism over 11 years has been harder to define.

He sided with the court’s majority in the landmark Citizens United case that allowed for unlimited independent corporate spending on elections, and he wrote the decision striking down the key section of the Voting Rights Act. But he twice rescued President Obama’s signature Affordable Care Act from annihilation, a task that Trump and the Republican Congress have vowed to take on.

Now a chief justice who endured a testy relationship with Obama faces a potentially stormy one with Trump, who prefers bold strokes to Roberts’ minimalist brand of jurisprudence.

Two Very Different Styles

The two conservative leaders could not be more different. Where Trump is bellicose, Roberts is circumspect. Given various opportunities to comment on Trump’s rhetoric or congressional Republicans’ refusal to fill Scalia’s seat throughout 2016, the chief justice demurred.

Ironically, Trump’s victory saved Roberts’ role as a powerful chief justice. With a conservative rather than a liberal replacing Scalia, Roberts will remain in the majority on most rulings, allowing him to decide who writes the opinions. Had Hillary Clinton won the White House, her nominee likely would have thrust Roberts into a conservative minority and empowered Justice Ruth Bader Ginsburg, the leader of the court’s liberal wing.

Now Trump and Senate Republicans will deliver Roberts a fifth conservative justice. If the new president chooses a hard-line conservative such as Alabama’s William Pryor, who serves on the U.S. Court of Appeals for the 11th Circuit, it could push Roberts further toward the middle. And if Justice Anthony Kennedy, the court’s swing vote, retires while Trump is president, Roberts could become the court’s least reliable conservative.

“It does put him in a position where he can have a lot of influence, not only because he’s chief justice, but because of where he sits on the court,” Gorod says.

Supreme Court justices serve lifetime appointments, so their tenure usually traverses several presidencies. For Roberts, the billionaire real estate magnate will be his third — following George W. Bush, who named him chief justice, and Obama, who voted against him in the Senate.

Roberts cut a modest figure before the Senate Judiciary Committee when making his case in September 2005. “It’s my job to call balls and strikes, and not to pitch or bat,” he assured lawmakers. The Senate rewarded him with a 78-22 confirmation vote, a better percentage than the justices who have followed.

His eight-year relationship with Obama began on a low note, when Roberts botched the oath of office before more than 1.8 million people who crowded the National Mall. To prevent a far-fetched challenge to Obama’s presidency, the two repeated the oath inside the White House on Jan. 21.

But Obama and Vice President Biden went out of their way to establish a relationship with the conservative-leaning court by visiting the justices a few days before the inauguration, something Trump and Vice President-elect Mike Pence have not done because of conflicting schedules. On Thursday afternoon, Roberts met briefly with Trump at Blair House, across from the White House, to go over Friday’s arrangements.

Brickbats and Bailouts

There were troubles to come: In his 2010 State of the Union address, with Roberts in the front row of the House of Representatives, Obama criticized the court’s Citizens United decision to whoops of applause from Democrats. Roberts later described the experience as “very troubling” and questioned whether justices should continue to attend an annual ritual that has “degenerated into a political pep rally.”

In 2013, during the first round of Supreme Court debates over same-sex marriage, Roberts asked Solicitor General Donald Verrilli why the president would continue to enforce the Defense of Marriage Act while asking the justices to strike it down. “I don’t see why he doesn’t have the courage of his convictions,” Roberts said.

But in 2012 and again in 2015, the chief justice bailed out Obama’s signature health care law, ensuring the president would leave office with his biggest achievement largely intact. “Congress passed the Affordable Care Act to improve health insurance markets, not to destroy them,” Roberts said in 2015.

While the first ruling saved the law and the second only its tax credits, both bore Roberts’ distinctive brand of jurisprudence. The court should not stick its neck too far out, he believes, deferring to the other branches of government wherever possible. It caused Scalia to quip that the law should be called “SCOTUScare.”

The chief justice’s pragmatic view often aligned Roberts with the moderate judge Obama sought as Scalia’s replacement, Merrick Garland. The two served together on the U.S. Court of Appeals for the D.C. Circuit 2003-05 and agreed on 85% of the cases they shared. When they differed, however, it was usually over federal power — and there, Roberts’ skepticism of executive branch authority could jibe with Trump’s, who has vowed to scale back on Obama’s use of executive actions.