President Obama on Saturday nominated U.S. Attorney Loretta Lynch as his next attorney general. If confirmed, she would be the first African American woman to serve in that post.

Lynch, 55, is an experienced prosecutor with deep relationships inside the Justice Department and a long history of litigating political corruption, terrorism and organized crime cases.

“Ms. Lynch is a strong, independent prosecutor who has twice led one of the most important U.S. Attorney’s Offices in the country,” White House press secretary Josh Earnest said in a statement Friday. “She will succeed Eric Holder, whose tenure has been marked by historic gains in the areas of criminal justice reform and civil rights enforcement.” Holder and Lynch joined Obama in the Roosevelt Room for Saturday’s announcement.

Lynch was the least controversial of the final choices before the president, according to several government officials. She has been confirmed twice by the Senate. And she was respected for the way she conducted several high-profile cases without seeking ­publicity.

Still, the nomination could spark a battle on Capitol Hill. Republicans warned before the midterm election said they opposed the idea of approving a nomination in a lame-duck session of Congress. Democrats, however, may choose to have the confirmation fight while they still have control of the Senate.

U.S. Attorney Loretta E. Lynch in July. (Reuters)

Sen. Charles E. Grassley (R-

Iowa), who is expected to be the new chairman of the Senate Judiciary Committee, said Friday he expected Lynch to get a “very fair but thorough vetting” from the committee.

“U.S. attorneys are rarely elevated directly to this position, so I look forward to learning more about her, how she will interact with Congress and how she proposes to lead the department,” said Grassley, who has tangled repeatedly with Holder. “I’m hopeful that her tenure, if confirmed, will restore confidence in the attorney general as a politically independent voice for the American people.”

Sen. Mitch McConnell (R-Ky.), who is expected to be the next Senate majority leader, said: “Ms. Lynch will receive fair consideration by the Senate. And her nomination should be considered in the new Congress through regular order.”

Lynch, who had been rumored for weeks to be a leading contender to replace Holder, chairs the Justice Department review commission that has advised Holder on policy decisions. In that capacity, she worked closely with several senior Justice officials, including former associate attorney general Tony West, who stepped down from his post in September.

“Loretta’s an excellent choice — smart, steady, talented and experienced,” West said in an interview Friday. “You’d be hard-pressed to come up with anyone better qualified or more prepared to be the nation’s next attorney general.”

Her appointments to be U.S. attorney for the Eastern District of New York — first from 1999 to 2001 under President Bill Clinton and again in 2010 — each had to be confirmed by the Senate.

“She’s the wonderful combination of smart, focused, personable and kind,” said Robert Raben, an assistant attorney general who worked with Lynch in the Clinton administration and is now a Washington consultant and lobbyist. “She’s a great pick — law enforcement and prosecution chops and a deep sense of compassion. That she is an African American woman from the South is just an awesome day for this nation.”

The daughter of a Baptist minister, Lynch grew up in Greensboro, N.C. She received a bachelor’s degree from Harvard College and a law degree from Harvard Law School.

During her first term in the post, Lynch oversaw the prosecution of New York police officers for brutality against Abner Louima, a Haitian immigrant who was arrested after a scuffle outside a nightclub. She is now prosecuting Rep. Michael G. Grimm (R-N.Y.), who was reelected Tuesday, for alleged fraud.

Her team also helped investigate Citigroup’s sales of mortgage securities, a probe that culminated in a $7 billion settlement between the bank and federal authorities.

At a recent goodbye ceremony for West in the Great Hall at Justice Department headquarters, Lynch spoke publicly about the “tug of war” between U.S. attorneys in the field and the headquarters in Washington. But she praised West for working closely with the U.S. attorneys and listening to their needs.

Lynch enjoys the strong support of Democrats and progressive activists.

Nan Aaron, president of the Alliance for Justice, which represents a coalition of 100 liberal groups, cheered the prospect of Lynch’s nomination in a statement. “We are confident that Lynch will build on Holder’s strong legacy of standing up for civil rights and ensuring equal justice for all Americans,” she said. “We call on Ms. Lynch to take a leading role in addressing the Supreme Court’s repeated efforts to deny access to the courts and the ballot box.”

Hill Republicans were more skeptical but expressed hope that their relationship with Lynch would be better than with it is with Holder.

“When reviewing a candidate to serve as our nation’s chief law enforcement officer, a full and fair confirmation process is always essential, and its importance has only increased in light of the troubling abuses under the current Attorney General,” Sen. Orrin G. Hatch (R-Utah), the longest-serving member of the judiciary panel, said in a statement. “I look forward to hearing Ms. Lynch’s plans for restoring trust in the Department of Justice.”

Obama had initially planned to announce Lynch’s nomination when he returned from a week-long trip to Asia that starts Sunday, government officials said. Earnest initially discounted media reports about the Lynch selection. But after reporters continued to pursue the subject, the White House moved up the announcement to Saturday.

“Loretta Lynch is a consummate professional, has a first-rate legal mind and is committed in her bones to the equal application of justice for all people,” said Sen. Charles E. Schumer (D-N.Y.), a close White House ally. “I was proud to recommend her to be the U.S. attorney for my home community of the Eastern District of New York, and I will be prouder still to champion what must be her swift confirmation in the Senate.”

Ed O’Keefe contributed to this report.