WASHINGTON — President Barack Obama this weekend will begin to dig into lengthy and in-depth briefing documents detailing the background and experience of potential nominees to fill the pivotal U.S. Supreme Court vacancy, the White House said on Friday.

Obama has phoned Senate leaders in the past day, including Republicans who have threatened to block any nominee made by the Democratic president to replace long-serving conservative Justice Antonin Scalia, who died on Feb. 13.

The court’s ideological balance of power is at stake, and Obama’s nominee could tip it to the left for the first time in decades. Scalia’s death left the court with four conservative and four liberal justices.

Obama made it clear in his calls with two key Senate Republicans, Majority Leader Mitch McConnell and Judiciary Committee Chairman Chuck Grassley, that he will nominate someone for the job, his spokesman Josh Earnest told reporters.

McConnell has said the seat should remain vacant until Obama’s successor takes office next January so voters can have a say in the selection when they choose a new president in the Nov. 8 election.

“The president’s team, over the course of this week, has spent a lot of time preparing materials for the president’s review, and I would expect, over the weekend, that the president will begin to dig into the materials that have been prepared for him,” Earnest said.

Earnest gave no clues about whom Obama might pick but said the lengthy briefing materials included information about “some potential nominees” including career accomplishments and experience.

Obama also spoke with Senate Democratic Leader Harry Reid and Sen. Patrick Leahy, the Judiciary Committee’s top Democrat, Earnest said.

Reid said on Thursday after speaking with Obama that he expected the president to name his pick in “a little over three weeks.” Earnest declined to discuss a timetable for Obama’s decision, and said the president’s staff had not yet provided a “short list” of candidates.

Earnest said Obama would consult “a wide variety of individuals with a wide variety of perspectives” as he weighs his decision.