WASHINGTON (AP) — A federal judge nominated to the nation's second-most powerful court said Wednesday that he was writing as an academic and commentator when he criticized as "indefensible" a Supreme Court ruling upholding the Affordable Care Act.

Justin Walker, a 37-year-old protege of Senate Majority Leader Mitch McConnell and Supreme Court Justice Brett Kavanaugh, said he will have an open mind on the Obama-era health care law if it comes before him as a district or appeals court judge. At a hearing on his nomination to a seat on the U.S. Court of Appeals for the District of Columbia Circuit, Walker declined a request by Senate Democrats to recuse himself on matters related to the health-care law if he's confirmed.

Walker said he was "an academic and a citizen engaged in the public sphere" when he wrote a 2018 article calling Chief Justice John Roberts' opinion upholding the health care law "indefensible" and "catastrophic.'' Walker said he would be bound by the ruling as precedent and would consider any challenge to it with an open mind.

Democrats say Walker's confirmation could threaten the health of millions of Americans protected by the law, which the Trump administration is challenging in court.

"After 162 TV appearances and all you've written (on the health care law), it's painful to hear you say you have an open mind,'' Sen. Dick Durbin, D-Ill., told Walker.

He and other Democrats complained that McConnell, the Kentucky Republican who leads the Senate, had called the chamber back into session to consider Walker's nomination, despite a stay-at-home order in Washington amid the coronavirus crisis. The seat Walker would take will not be vacant until September.

"It's indefensible that we're here to confirm someone who would dismantle the health care law that is saving millions of lives,'' said Sen. Richard Blumenthal, D-Conn.

Blumenthal and Durbin were among the few Democrats who attended the hearing in person. Most were connected to the meeting through a video link.

None of the senators wore masks, and Walker's face was uncovered throughout the hearing, which lasted 2 1/2 hours.

Walker also was asked about comments he made during a speech in March, celebrating his recent confirmation as a judge, in which he lavished praise on Kavanaugh, who was confirmed to the Supreme Court in 2018 after a bitter partisan fight over allegations of sexual assault and other claims. Walker clerked for Kavanaugh when he was on the appeals court to which Walker is nominated.

Walker compared Kavanaugh to St. Paul — "persecuted but not abandoned" — and said, "In Kavanaugh's America, we will not surrender while you wage war on our work, or our cause, or our hope, or our dream.'' The speech, in Louisville, Kentucky, was attended by McConnell, Kavanaugh and other conservative luminaries.

"What war is Justice Kavanaugh waging?" asked Sen. Sheldon Whitehouse, D-R.I.

Walker said he was describing the kind of judge Kavanaugh is, adding that he will defend Kavanaugh and former Supreme Court Justice Anthony Kennedy — another mentor — "until the cows come home.''

In his speech, Walker referred to his values as ones progressives might call "deplorable," a reference to Democrat Hillary Clinton's criticism of President Donald Trump's supporters.

"We are winning, but we have not won,'' Walker said.

Walker drew a "Not Qualified" rating from the American Bar Association when Trump nominated him last year to be a federal judge in Kentucky. The group changed its rating this week, calling him "Well Qualified" to serve on the appeals court.

"Based on interviews and a review of his scholarship and other writings, the (ABA's) Standing Committee believes that Judge Walker possesses a keen intellect, and his writing ability is exemplary,'' the group wrote in a letter Tuesday to the Senate Judiciary Committee.

The letter cited Walker's experience as a clerk to Kavanaugh and Kennedy and his six months as a federal trial judge. Walker, a graduate of Duke University and Harvard Law School, was confirmed as a judge last year. He previously was a lawyer in Louisville and Washington.

McConnell said Wednesday that his protege and family friend "possesses a generational legal mind, a kind heart and total judicial impartiality.''

"President Trump made an outstanding choice when he asked this Kentuckian to take his public service to the next level. I am confident Judge Walker will not disappoint,'' McConnell added.

Liberal groups were incensed at Walker's nomination for a quick promotion to the nation's second-highest court. More than 200 groups, including the Leadership Conference on Civil and Human Rights, the NAACP and the National Council on Jewish Women oppose Walker's nomination, citing his record against expanding access to health care and against safeguards for the environment, consumers and the workplace.

Senate Democratic Leader Chuck Schumer said Walker "has more experience as a cable news commentator than he does trying cases in court.''

Walker's qualifications "pale in comparison to those of previous nominees to the D.C. Circuit" by presidents of both parties, Schumer said. "Nominees by Democratic presidents and Republican presidents all were deeply steeped in the law, just about every one. What Leader McConnell is doing to the courts is nothing short of disgraceful.''