President Trump’s potential Supreme Court nominees could face a slog through the confirmation process. (Evan Vucci/AP)

President Trump’s potential Supreme Court nominees tend to fall into two categories.

One set of possible picks hails from a throwback era, having won confirmation to their federal court posts by overwhelming votes last decade with the support of dozens of Democrats still serving today in the Senate.

Then there’s another cluster who just went through the more modern confirmation process — highly partisan with almost no Democratic support — to secure seats on the federal appeals court.

There are several other possibilities, including Sen. Mike Lee (R-Utah), whom Trump interviewed Monday, but by and large the leading candidates to replace Justice Anthony M. Kennedy come from the federal bench.

More than half of the 25 names on Trump’s list come from the appellate courts, including four whom he interviewed Monday. That follows the tradition of the last 32 years of finding the next justice from those circuit courts, to the point where eight of the nine current members on the high court served on an appellate court.

But Trump’s potential picks have a sharp divide between those with a long service on the circuit courts and those who are brand new, setting up what could be very different confirmation battles in terms of the contours of the fight.

If the choice comes from the first group, it might become “a more traditional fight” that focuses on the dozen or so years of judicial opinions written off that bench on the hot-button issues of the day, according to Chris Kang, chief counsel for Demand Justice, a group that is leading the liberal coalition in opposition to Trump’s selection.

If the choice comes from the newer crop of judges, the showdown would turn into a higher-profile replay of recent confirmations that focused less on judicial opinions and more on qualifications and personal background.

Either way, both sides in the fight are ready to pounce once Trump makes the selection because the stakes are so high, given Kennedy’s role as a swing vote. The nominee should expect a tough fight from the Senate Judiciary Committee all the way through a confirmation vote.

“The playbook is pretty much set,” said Carrie Severino, chief counsel of the Judicial Crisis Network, the conservative group serving as central promoter of the nominee.

“People view this as a clean slate,” Kang said.

His group has a $5 million budget, so far, to try to define the nominee. Severino said her group would at least match the $10 million spent supporting the confirmation of Justice Neil M. Gorsuch in 2017. “Whatever it takes,” she said.

That serves as a warning shot to those judges who easily won confirmation last decade. It may sound like a time from 30 years ago that senators got along well and supported one another’s preferences for judicial nominations, but just 11 years ago Thomas Hardiman won confirmation to the U.S. Circuit Court of Appeals for the 3rd Circuit on a 95-to-0 vote.

Based in Pittsburgh, Hardiman received praise from his state’s Democratic senator, Robert P. Casey Jr. (Pa.), who praised the judge’s “solid record” as a district court judge who was “well qualified” for his promotion.

Raymond Kethledge’s nomination to the Court of Appeals for the 6th Circuit did not even require a roll call, simply passing on a voice vote in 2008. It took more than two years for him to coast to that vote, but that was because of an unrelated dispute over another judicial nomination. When it came time for his hearing, Sen. Debbie Stabenow (D-Mich.) was on hand to introduce him and other Michigan nominees to the committee.

Trump interviewed Kethledge on Monday, and Hardiman was widely considered the runner-up to Gorsuch in the 2017 selection process. If either is selected now, the focus would be on what they have written as high-level judges.

Liberal opponents intend to focus heavily on rulings regarding health-care and abortion rights. The Trump administration’s decision not to defend the Affordable Care Act from a constitutional challenge in Texas, Kang said, makes any rulings related to that law and health-care more broadly “a real live issue.”

That Bush White House era had its share of judicial wars, as Democrats filibustered several appellate court selections, but a bipartisan deal in 2005 cooled the tempers in the Senate until 2013, when Democrats had the majority and unilaterally changed rules to eliminate the 60-vote threshold for filibusters to end debate on most judicial nominees.

Republicans followed suit in 2017 to extend the rule change to Supreme Court nominees, and over the past five years most judges confirmed to the circuit courts have endured highly partisan showdowns that resemble mini-Supreme Court battles.

“If you had nominated Amy Coney Barrett in 2004, you would’ve had a very different confirmation process,” Severino said.

Instead, Barrett won confirmation to the Court of Appeals for the 7th Circuit last year with just 55 votes, including three Democrats. After a contentious hearing that included questions about her Catholic faith and her writings as a law professor at the University of Notre Dame, Republicans accused Democrats of bias against Catholics.

Confirmed on Oct. 31, Barrett has been a judge for only eight months, making any nomination battle a likely do-over of last year’s fight.

Amul R. Thapar would have the most narrow path to winning a Supreme Court confirmation: Not a single Democrat voted to confirm him in May 2017 to the Court of Appeals for the 6th Circuit.

“They’re not going to be able to turn around and vote for him for Supreme Court,” Kang said.

Barrett and Thapar both interviewed with Trump on Monday. The other appellate jurist to meet Trump was Brett M. Kavanaugh, whose 2006 confirmation to the U.S. Circuit Court of Appeals for the District of Columbia came after a brutal slog that more closely resembled the 2017 nominations.

In the 1990s, Kavanaugh served as an investigator for Kenneth Starr’s independent counsel investigation of President Clinton, then worked as a top lawyer in the Bush West Wing. He faced questions about his Starr days and any role related to enhanced interrogation techniques.

Kavanaugh, who once clerked for Kennedy, won confirmation, 57 to 36, with just four Democrats supporting him — which might serve as good preparation for the brutal process he would endure 12 years later if Trump chooses him to succeed his mentor.

Correction: An earlier version of this story misidentified the appeals court on which Amul R. Thapar serves. It is the 6th Circuit, not the 10th Circuit.

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