WASHINGTON — Republicans are intensifying their attacks on Judge Ketanji Brown Jackson after weeks of publicly reserving judgment on President Biden’s Supreme Court nominee, ahead of historic hearings on the first Black woman to be put forward as a justice.

Republican leaders, wary of engaging in a potentially racially charged spectacle that could prompt a political backlash, have promised a more dignified review of the latest Supreme Court candidate, after a series of bitter clashes over the court. But in recent days, with the approach of the Senate Judiciary Committee’s hearings on her nomination that begin on Monday, their tone has shifted.

Last week, Senator Josh Hawley, a Missouri Republican who sits on the panel and will question Judge Jackson, claimed his review of her judicial record had determined that she had been lenient in sentencing some sex offenders and those convicted of possessing child pornography. He also suggested that, as a member of the United States Sentencing Commission, she worked to reduce penalties for those caught with child pornography. A detailed background paper prepared for the Judiciary Committee made a similar case.

At the same time, Senator Mitch McConnell, Republican of Kentucky and the minority leader, has doubled down on his suggestion that Judge Jackson’s experience as a public defender could influence her view of the law and lead her to favor criminal defendants.

“Her supporters look at her résumé and deduce a special empathy for criminals,” Mr. McConnell said in a lengthy floor speech in which he argued that her work on behalf of the accused was a blot on her record. “I guess that means that government prosecutors and innocent crime victims start each trial at a disadvantage.”

The increasingly hostile critiques of Judge Jackson suggest that her confirmation hearings might not be the sober, drama-free proceeding that many had anticipated when she was nominated to replace Justice Stephen G. Breyer, who has announced he will retire at the end of the court’s current term this summer.

Her confirmation would not change the ideological composition of the court, which is tilted 6-3 toward conservatives. And Judge Jackson has previously been confirmed three times by the Senate for two judgeships and a spot on the sentencing commission. Nothing surfaced on those occasions to impede her approval. Republicans concede she has the legal experience and educational qualifications for the lifetime position.

Mr. Hawley, who is regarded as a potential Republican presidential contender and has not voted for a single Biden administration judicial nominee, was never considered a likely supporter of Judge Jackson. Still, his detailed takedown of her record on sex crimes has generated concern among Democrats, who worry it could deter some Republicans who are considering supporting her, or even rattle some senators in their own party, all of whom will likely be needed to win confirmation.

The White House and Senate Democrats have pushed back forcefully, accusing Mr. Hawley of intentionally disseminating misleading information and taking material out of context to paint a distorted picture of Judge Jackson’s record.

“Attempts to smear or discredit her history and her work are not borne out in facts,” said Jen Psaki, the White House press secretary.

Administration and Senate officials say that Judge Jackson’s sentences in pornography cases were at or above recommendations from probation officials and comparable to what other federal judges were handing down under guidelines that were considered badly outdated. They also point to her strong support from law enforcement groups and prominent police officials.

“Those individuals would be surprised to learn that they are supposedly ‘soft on crime’,” said Andrew Bates, a White House spokesman who has been working on the confirmation. He called Mr. Hawley’s allegations “toxic and weakly presented misinformation that relies on taking cherry-picked elements of her record out of context — and it buckles under the lightest scrutiny.”

As for the criticism of the sentencing commission, the White House and Senate Democrats note that the sentencing recommendations it made during Judge Jackson’s tenure were approved unanimously by the bipartisan panel, with members appointed by presidents of both parties and ultimately accepted by Congress.

One Republican-appointed jurist who served on the panel with Judge Jackson, Judge William H. Pryor Jr., the chief judge of the U.S. Court of Appeals for the 11th Circuit, confirmed that the recommendations of the commission were almost uniformly supported by all its members as the panel sought to eliminate disparities and improve sentencing.

“We worked by consensus, and that is the tradition of the sentencing commission,,” he said in an interview. “Virtually all of our votes were unanimous and data-driven.”

Judge Jackson’s service as a federal public defender, and her work for some detainees held at the U.S. prison at Guantánamo Bay, Cuba, was always going to be an issue in her confirmation. But Mr. Hawley’s accusation added a new element to the debate, focusing more on her time as a federal district court judge and a member of the sentencing commission. Other Republican members have said they intend to pursue the issue with Judge Jackson.

The days of broad bipartisan support for Supreme Court nominees are long gone, but Democrats have held out hope that Judge Jackson could get at least a handful of Republican votes given her experience and the possibility that some would want to be counted in support of placing a Black woman on the court.

But just three Republicans backed her last year when she was confirmed to the U.S. Court of Appeals for the District of Columbia Circuit, and persuading senators to support a candidate for a higher court after opposing her for a lower one is a difficult task.

Still, Judge Jackson, with her White House entourage in tow, has engaged in a charm offensive in the Senate, meeting with 44 senators of both parties and all 22 members of the evenly divided Judiciary Committee.

Democrats have been effusive in their praise and support of Judge Jackson, calling her an ideal candidate for the court with the capacity to work with other justices to try to develop more consensus rulings.

Republicans who have met with her report privately that she is very engaging, presents a memorable life story of achievement and speaks admiringly of Justice Antonin Scalia’s view that judges should interpret, not make the law. But they say they have also been frustrated by her unwillingness to lay out a specific judicial philosophy and her refusal to take a stance on whether the Supreme Court should be expanded, as progressive groups have proposed.

She will be pressed on those subjects and many more during questioning by senators on Tuesday and Wednesday, after a session on Monday in which each of them will deliver statements, Judge Jackson will be introduced, and she will make opening remarks.

Despite the historic nature of her nomination, Supreme Court confirmations have become intense struggles, and the recent shift in tone among Republicans suggests this week’s proceedings could be no different.

Given the increasing role of the court in settling political and social questions, activists on both sides of the ideological spectrum are deeply invested in its makeup. Democrats are still livid at Republicans’ blockade of Merrick B. Garland, President Barack Obama’s 2016 nominee to the court, and the rapid manner in which they rammed through the confirmation of Justice Amy Coney Barrett, former President Donald J. Trump’s pick, just before he lost the 2020 election.

Republicans remain irate about the confirmation hearings for Justice Brett M. Kavanaugh, which were marred by allegations of sexual assault.

Against that backdrop, Senate veterans say a fight over Judge Jackson is probably inevitable.

“It's a fact that we are now living in very partisan times,” said Senator Richard J. Durbin, Democrat of Illinois and the chairman of the Judiciary Committee, who will for the first time be overseeing a high court confirmation.