Ketanji Brown Jackson is not only the first Supreme Court justice confirmed under Joe Biden's presidency — but, perhaps, also his last, based on comments Senate Minority Leader Mitch McConnell made Thursday to Axios' Jonathan Swan.

Why it matters: During an Axios News Shapers interview, McConnell declined repeatedly to say whether he could commit to holding hearings on any Supreme Court nominee by President Biden if Republicans regain the Senate majority in November and a seat opens in 2023.

• "I choose not to answer the question," McConnell finally said, after repeated pressing.

Between the lines: 2023 is not an election year, and therefore doesn't fit under McConnell's "Merrick Garland" rule.

He used that construct to block President Obama's 2016 nomination of Garland by refusing to hold hearings for Supreme Court nominees during an election year in which the opposing party controls the Senate.

• What McConnell appears to be at least contemplating — refusing hearings no matter the stage of a presidency — is without precedent in recent American history.
• Asked whether he's developing an argument for not holding hearings if it isn't an election year ... McConnell declined to answer.

If a Majority Leader McConnell does this, it would create a new paradigm: No Supreme Court justice can be allowed a confirmation process — let alone be confirmed — when the opposition party controls the Senate.

• The result would be a Supreme Court with an even number of justices.
• And that would create the possibility of a deadlock on any number of issues, such as affirmative action, voting rights and religious liberty — for years.

The backstory: In 2016, McConnell made what he called a principled argument for not holding hearings on Garland — who held the same appellate court seat as Jackson.

• McConnell said it was an election year, and he would therefore wait until the next president was elected to hold any hearings. He said voters deserved to have a say in picking the next Supreme Court justice.
• The rest is history: McConnell blocked Obama from filling the vacancy left after the death of revered conservative Justice Antonin Scalia. Then Donald Trump surprised nearly everyone and beat Hillary Rodham Clinton in the 2016 presidential election.
• Instead of a liberal justice filling Scalia's seat, Trump appointed a strict constructionist conservative justice, Neil Gorsuch. Trump also was able to fill two more seats and change the balance of the court. It's now a 6-3 conservative majority.

The 80-year-old McConnell has said his decision to hold open the Scalia seat — despite tremendous opposition from the left — was the most consequential thing he's ever done.

• Few would doubt it.

The bottom line: Swan says, "I've done some difficult interviews over the past few years, including President Trump in the middle of a once-in-a-century pandemic. But McConnell might be the most challenging subject in American politics.

• "The Senate minority leader's usual tactic in interviews is to simply refuse to answer questions he doesn't like. He did this repeatedly Thursday. But unlike every other politician I've interviewed, McConnell remains utterly disciplined and refuses to answer, no matter from how many different angles one comes at him.
• "For a sense of this dynamic, watch this exchange in which I ask McConnell about his "moral red lines."
• "I asked McConnell how he could go from saying that former President Trump was "practically and morally responsible" for the Jan. 6 attack on the Capitol to, two weeks later, saying he would "absolutely" support Trump if he's the Republican presidential nominee in 2024.
• "McConnell's response tells you a lot about how he sees his political world," Swan said.

📺 Go deeper: Watch the whole 30-minute interview via this link.