Stuart Delery, the White House counsel who has helped usher in some of President Biden’s most important policies while defending him against Republican attacks, announced on Thursday that he plans to step down as the West Wing shapes its staff for the final 15-month sprint to next year’s election.

Mr. Delery had indicated to colleagues a few months ago that he would be ready to leave by fall after nearly three years in the White House and the pre-inaugural transition that have been all consuming. Since Republicans took over the House in January, the counsel’s office has been the command post for the White House’s response to a multitude of congressional investigations.

No successor was named on Thursday, but a new counsel was expected to be in place by the time Mr. Delery formally leaves next month. Jeffrey D. Zients, the White House chief of staff who took over the president’s team six months ago, has asked cabinet secretaries to decide in the coming weeks whether they plan to depart or will commit to staying through the November 2024 election to avoid distracting confirmations heading into the campaign season.

Mr. Biden’s White House team has been steadier than most, especially compared with the one under his predecessor, former President Donald J. Trump, who burned through aides at a frenetic pace. Although a number of top officials have left Mr. Biden’s administration, the total turnover of 56 percent remains below the modern average, and his cabinet is the most stable going back at least seven administrations, according to figures compiled by the Brookings Institution.

Susan E. Rice, the president’s domestic policy adviser, left in May and was replaced by Neera Tanden, the staff secretary, who in turn was replaced by Stefanie Feldman, a longtime Biden aide. Julie Chávez Rodríguez stepped down as director of intergovernmental affairs to take over as campaign manager and was succeeded by Tom Perez, a former labor secretary. Louisa Terrell, the director of legislative affairs who helped coordinate debt ceiling negotiations, announced her departure last month and was replaced by Shuwanza Goff, the president’s liaison to the House.

But the president’s core inner circle of Mr. Zients and advisers like Steven J. Ricchetti, Anita Dunn, Jennifer O’Malley Dillon and Bruce Reed is expected to remain intact through the election, as is his top national security team led by Jake Sullivan and his deputy, Jon Finer.

Some colleagues have speculated about whether Michael Donilon, one of Mr. Biden’s closest advisers and the author of many of his major speeches, will move over to the campaign or stay inside the White House.

Mr. Delery, 54, served as acting associate attorney general, the No. 3 official at the Justice Department, under President Barack Obama and joined the Biden team as deputy White House counsel before taking over the top legal job in the White House a little over a year ago. He is the first openly gay man to serve as counsel to the president.

“Stuart Delery has been a trusted adviser and a constant source of innovative legal thinking since Day 1 of my administration,” Mr. Biden said in a statement.

Mr. Delery, a low-key and studious Yale Law School graduate, was among the legal architects of some of Mr. Biden’s most important initiatives, including strategies to distribute Covid-19 vaccines, to forgive hundreds of billions of dollars of student debt and to revamp immigration after the expiration of Title 42, a pandemic-era measure.

When the Supreme Court overruled the president’s original student loan plan, his team quickly developed new ways to try to accomplish the same goals. When Republicans threatened to not raise the debt ceiling, Mr. Delery developed options for Mr. Biden to do so on his own authority, although it proved unnecessary when a bipartisan deal was struck.

Mr. Delery also oversaw a drive to install as many judges as possible. During his tenure, 20 nominees were confirmed to federal appeals courts and 51 to federal district courts. The slate of new judges has been the most diverse in history.

“Stuart Delery was a historic counsel for an administration getting historic things done,” Mr. Zients said in a statement. “His work in support of President Biden and Vice President Harris will shape the country for the better for decades to come.”