President Biden’s commission to examine changes to the Supreme Court is a move to placate his base, which is agitating to add liberal justices to the conservative-leaning court, according to court watchers.

But liberals are split on whether any real court-packing will result from the president’s panel.

“There is nothing productive that is going to come from this,” said Josh Blackman, a professor at South Texas College of Law. “If anything, this report will probably counsel against expanding the court.”

The panel will examine “the length of service and turnover of justices on the Court; the membership and size of the Court; and the Court’s case selection, rules, and practices,” among other topics, the White House said.

The commission will issue a report after considering the positives and negatives of adding justices to the court.

Senate Minority Leader Mitch McConnell of Kentucky and other Republicans expressed wariness about Mr. Biden’s intentions. Mr. McConnell called the president’s move “a direct assault on our nation’s independent judiciary and yet another sign of the Far Left’s influence over the Biden administration.”

“Rational observers know well there is nothing about the structure or operation of the judicial branch that requires ‘study,” Mr. McConnell said. “The president spent most of his campaign playing coy on the issue but has now admitted from the safety of a four-year term that he views the judiciary as ‘out of whack.’ This is not some new, serious or sober pivot away from Democrats’ political attacks on the court. It’s just an attempt to clothe those ongoing attacks in fake legitimacy.”

Mr. Biden resisted calls during the 2020 campaign to embrace an expansion of the Supreme Court, as many on the left advocated. Vice President Kamala Harris said during the Democratic presidential primary race that she was open to the idea of adding justices.

Instead, Mr. Biden said he would appoint a commission to explore the idea — typically Washington-speak for sidelining issues deemed too hot or sensitive to handle.

“Biden is trying to do something to placate the base,” Mr. Blackman said. “A delay tactic.”

Sen. Roy Blunt, Missouri Republican, said Sunday that he would prefer to leave nine justices on the court.

“I hope what the president is doing here is looking at this objectively,” Mr. Blunt said on Gray TV’s “Full Court Press with Greta Van Susteren.” “I have some concerns, though, that this puts the court in a much more partisan and political place than the court needs to be.”

Sen. Ben Sasse, Nebraska Republican, said the president knows his court-packing commission isn’t going anywhere.

“President Biden knows that he doesn’t even have the votes in his own party to pack the court, he knows that court-packing is a nonstarter with the American people, and he knows that this commission’s report is just going to be a taxpayer-funded door stopper. What the president doesn’t have is the courage to come out and flatly tell the radical left that he’s not going to pack the Supreme Court,” Mr. Sasse said.

The Supreme Court has had nine justices since 1869. Before that, it fluctuated from five to 10 justices.

The Constitution does not set a number of justices for the high court, but any expansion would have to go through Congress, said Curt Levey, president of the Committee for Justice.

Given the 50-50 party-line split in the Senate and a 60-vote threshold to pass most legislation, it’s unlikely any bill to add justices would pass.

Mr. Levey said proposed term limits for the justices could be unconstitutional, given that scholars have interpreted the Constitution to give judges lifetime appointments.

Conservative activists, though, warn that the president’s move is a first step toward expanding the court.

“This makes clear that President Biden and the Democratic Party seek to change the rules to advance their far-left agenda,” said Adam Brandon, president of FreedomWorks, a center that advocates for small government.

Kelly Shackelford, president of First Liberty Institute, said the left is trying to politicize the Supreme Court for their advantage.

“The last thing we need in this country right now is a Supreme Court coup,” he said.

Carrie Severino, president of the Judicial Crisis Network, said Mr. Biden’s commission is just a “fig leaf” and that he will likely move to pack the court.

“Biden’s position on that is 100% determined by his political calculus,” she said, adding that the president’s liberal dark-money donors have been advocating for a court expansion for years.

The commission is supposed to complete a report within 180 days of its first public meeting.

The announcement was made as liberal activists were ramping up pressure for Justice Stephen G. Breyer to retire so Mr. Biden could choose a replacement.

Justice Breyer, a Clinton appointee, said last week that expanding the court could erode trust. Court watchers say the timing of Mr. Biden’s executive order is correlated to the outrage over Justice Breyer’s comments.

Aaron Belkin, director of the advocacy group Take Back the Court, said six months is too long to wait for recommendations.

“The solution is already clear,” Mr. Belkin said. “Adding seats is the only way to restore balance to the court, and Congress should get started right away.”

Liberals want to add seats so a Democratic president can appoint justices and theoretically rebalance what is currently a 6-3 conservative majority.

Many on the left said Mr. Biden’s order for a commission is a step in the right direction.

“From ensuring the lower courts have sufficient resources to administer justice, to ensuring a bench with judges from diverse personal and professional backgrounds, to addressing barriers to court access, there are serious challenges to the judiciary’s ability to function and deliver justice for all in America that must be addressed,” said Elizabeth Wydra, president of the Constitutional Accountability Center.