As Ketanji Brown Jackson became the president’s first appellate judge, Senator Mitch McConnell suggested he would block a Biden Supreme Court pick in 2024 if Republicans gained the majority.The Senate confirmed Judge Ketanji Brown Jackson on Monday to the influential U.S. Court of Appeals for the District of Columbia Circuit, giving President Biden his first pick on an appeals court even as the Senate Republican leader threatened future roadblocks for Biden administration judicial nominees.Following her approval by a bipartisan vote of 53 to 44, Judge Jackson, who served as a federal district judge, will join the court regarded as the second highest in the land, and considered an incubator for Supreme Court justices. She is widely considered a potential nominee for the Supreme Court should a vacancy occur during the tenure of Mr. Biden, who has promised to appoint the first African-American woman as a justice.“She has all the qualities of a model jurist,” Senator Chuck Schumer, Democrat of New York and the majority leader, said as he urged her approval. “She is brilliant, thoughtful, collaborative and dedicated to applying the law impartially. For these qualities, she has earned the respect of both sides.”Her approval came as Senator Mitch McConnell of Kentucky, the Republican leader, threatened to open a new front in the judicial wars that have rocked the Senate for decades. In an interview with the conservative radio commentator Hugh Hewitt, Mr. McConnell said Republicans would most likely block any Supreme Court nominee put forward by Mr. Biden in 2024 if Republicans regained control of the Senate in next year’s elections and a seat came open.“I think in the middle of a presidential election, if you have a Senate of the opposite party of the president, you have to go back to the 1880s to find the last time a vacancy was filled,” Mr. McConnell said. “So I think it’s highly unlikely.”His position was not surprising, since it was in line with his refusal in 2016 to consider President Barack Obama’s Supreme Court nomination of Merrick B. Garland, now the attorney general, saying it was too close to the presidential election even though the vacancy occurred in February. But it was nevertheless striking, given that Mr. McConnell was the architect of the strategy that allowed former President Donald J. Trump to fill a Supreme Court vacancy in the final six weeks before he stood for re-election.As for what would happen if a seat became open in 2023 and Republicans controlled the Senate, Mr. McConnell stopped short of declaring that he would block Mr. Biden from advancing a nominee so long before the election, but he left the door open to the possibility. “Well, we’d have to wait and see what happens,” Mr. McConnell said.Stonewalling a nominee in the year before a presidential election would amount to a significant escalation in the judicial wars.Senator Mitch McConnell, the Republican minority leader, said he is likely to block any Supreme Court nominee put forward by President Biden in 2024 if his party regains control of the Senate next year.Stefani Reynolds for The New York TimesMr. McConnell’s pronouncements will most likely amplify calls from progressive activists for Justice Stephen G. Breyer to retire while Democrats hold the Senate and can push through a successor. Justice Breyer, 82, an appointee of President Bill Clinton, has resisted calls to step aside. Justices often time their retirements to the end of the court’s term, which comes in two weeks.Mr. McConnell’s position in 2016 stood in stark contrast to the one he took last year when Senate Republicans, still in the majority, rushed through the confirmation of Justice Amy Coney Barrett just days before the presidential election, racing to fill the vacancy created by the death in September of Justice Ruth Bader Ginsburg..css-1xzcza9{list-style-type:disc;padding-inline-start:1em;}.css-3btd0c{font-family:nyt-franklin,helvetica,arial,sans-serif;font-size:1rem;line-height:1.375rem;color:#333;margin-bottom:0.78125rem;}@media (min-width:740px){.css-3btd0c{font-size:1.0625rem;line-height:1.5rem;margin-bottom:0.9375rem;}}.css-3btd0c strong{font-weight:600;}.css-3btd0c em{font-style:italic;}.css-w739ur{margin:0 auto 5px;font-family:nyt-franklin,helvetica,arial,sans-serif;font-weight:700;font-size:1.125rem;line-height:1.3125rem;color:#121212;}#NYT_BELOW_MAIN_CONTENT_REGION .css-w739ur{font-family:nyt-cheltenham,georgia,’times new roman’,times,serif;font-weight:700;font-size:1.375rem;line-height:1.625rem;}@media (min-width:740px){#NYT_BELOW_MAIN_CONTENT_REGION .css-w739ur{font-size:1.6875rem;line-height:1.875rem;}}@media (min-width:740px){.css-w739ur{font-size:1.25rem;line-height:1.4375rem;}}.css-9s9ecg{margin-bottom:15px;}.css-16ed7iq{width:100%;display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-align-items:center;-webkit-box-align:center;-ms-flex-align:center;align-items:center;-webkit-box-pack:center;-webkit-justify-content:center;-ms-flex-pack:center;justify-content:center;padding:10px 0;background-color:white;}.css-pmm6ed{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-align-items:center;-webkit-box-align:center;-ms-flex-align:center;align-items:center;}.css-pmm6ed > :not(:first-child){margin-left:5px;}.css-5gimkt{font-family:nyt-franklin,helvetica,arial,sans-serif;font-size:0.8125rem;font-weight:700;-webkit-letter-spacing:0.03em;-moz-letter-spacing:0.03em;-ms-letter-spacing:0.03em;letter-spacing:0.03em;text-transform:uppercase;color:#333;}.css-5gimkt:after{content:’Collapse’;}.css-rdoyk0{-webkit-transition:all 0.5s ease;transition:all 0.5s ease;-webkit-transform:rotate(180deg);-ms-transform:rotate(180deg);transform:rotate(180deg);}.css-eb027h{max-height:5000px;-webkit-transition:max-height 0.5s ease;transition:max-height 0.5s ease;}.css-6mllg9{-webkit-transition:all 0.5s ease;transition:all 0.5s ease;position:relative;opacity:0;}.css-6mllg9:before{content:”;background-image:linear-gradient(180deg,transparent,#ffffff);background-image:-webkit-linear-gradient(270deg,rgba(255,255,255,0),#ffffff);height:80px;width:100%;position:absolute;bottom:0px;pointer-events:none;}.css-uf1ume{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-box-pack:justify;-webkit-justify-content:space-between;-ms-flex-pack:justify;justify-content:space-between;}.css-wxi1cx{display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-flex-direction:column;-ms-flex-direction:column;flex-direction:column;-webkit-align-self:flex-end;-ms-flex-item-align:end;align-self:flex-end;}.css-12vbvwq{background-color:white;border:1px solid #e2e2e2;width:calc(100% – 40px);max-width:600px;margin:1.5rem auto 1.9rem;padding:15px;box-sizing:border-box;}@media (min-width:740px){.css-12vbvwq{padding:20px;width:100%;}}.css-12vbvwq:focus{outline:1px solid #e2e2e2;}#NYT_BELOW_MAIN_CONTENT_REGION .css-12vbvwq{border:none;padding:10px 0 0;border-top:2px solid #121212;}.css-12vbvwq[data-truncated] .css-rdoyk0{-webkit-transform:rotate(0deg);-ms-transform:rotate(0deg);transform:rotate(0deg);}.css-12vbvwq[data-truncated] .css-eb027h{max-height:300px;overflow:hidden;-webkit-transition:none;transition:none;}.css-12vbvwq[data-truncated] .css-5gimkt:after{content:’See more’;}.css-12vbvwq[data-truncated] .css-6mllg9{opacity:1;}.css-qjk116{margin:0 auto;overflow:hidden;}.css-qjk116 strong{font-weight:700;}.css-qjk116 em{font-style:italic;}.css-qjk116 a{color:#326891;-webkit-text-decoration:underline;text-decoration:underline;text-underline-offset:1px;-webkit-text-decoration-thickness:1px;text-decoration-thickness:1px;-webkit-text-decoration-color:#326891;text-decoration-color:#326891;}.css-qjk116 a:visited{color:#326891;-webkit-text-decoration-color:#326891;text-decoration-color:#326891;}.css-qjk116 a:hover{-webkit-text-decoration:none;text-decoration:none;}Republicans who had banded together in 2016 at Mr. McConnell’s urging and declared that it was not appropriate to confirm a Supreme Court nominee during an election year had remarkable conversions in the case of Judge Barrett. The Republican leader insisted that he had not changed his position, arguing that because Mr. Obama was a Democrat, it was entirely appropriate for members of his party to block his nominee.“What was different in 2020 was we were of the same party as the president,” Mr. McConnell told Mr. Hewitt. “And that’s why we went ahead with it.”Mr. McConnell’s decision to block Mr. Obama from filling the vacancy caused by the death of Justice Antonin Scalia was widely credited with encouraging conservatives to rally around Mr. Trump for the presidency, and ultimately allowing him to name three justices to the court, which now has a 6-to-3 conservative majority.Working in concert with the White House, Mr. McConnell and Senate Republicans also installed 54 conservative judges on the nation’s federal appeals courts, leaving Mr. Biden and Senate Democrats with significant ground to make up as they try to compensate for the conservative success of the Trump era.Senator Richard J. Durbin, Democrat of Illinois and chairman of the Judiciary Committee, called Judge Jackson “the first of many circuit court nominees we will confirm in this Congress.”Judge Jackson will now claim a seat on a court that is particularly prominent because of its routine involvement in Washington policy disputes and national security matters. She and other pending judicial nominees are part of a concerted effort by the Biden administration to diversify the federal courts, both in terms of the nominees themselves and their professional backgrounds.Judge Jackson counted being a public defender among her multiple legal jobs before becoming a federal judge, a role that her supporters note is different from the prosecutorial experience of many sitting on the federal bench.“Our judiciary has been dominated by former corporate lawyers and prosecutors for too long, and Judge Jackson’s experience as a public defender makes her a model for the type of judge President Biden and Senate Democrats should continue to prioritize,” said Christopher Kang, the chief counsel for the progressive group Demand Justice.Such experience has been an obstacle for judicial nominees in the past, and Republican opponents raised questions about her defense work at her confirmation hearing.Judge Jackson will replace Mr. Garland, who remained on the appellate court after his Supreme Court nomination was stymied before becoming attorney general. Mr. Biden has not named his choice for a second vacancy on the prestigious appeals court. More