In reactions mirroring the ideological split of the Supreme Court justices in their ruling granting presidents immunity for official actions, Republicans expressed triumph on Monday and Democrats dismay.
Senator J.D. Vance of Ohio was the first of former President Donald J. Trump’s top running-mate contenders to weigh in, calling the decision “a massive win, not just for Trump but the rule of law.”
Other Republicans also praised the ruling as a rejection of what they characterized as Democrats’ using the government against Mr. Trump for political purposes.
Senator Steve Daines of Montana, who leads Republicans’ Senate campaign arm, said the Supreme Court had ended a “sad chapter of Joe Biden’s weaponization of the Justice Department.” Stephen Miller, a top Trump adviser, called the decision “another setback for the Democrat Party’s illegal and unconstitutional crusade to outlaw dissent, jail the opposition leader, impose authoritarian rule, replace democracy with the deep state and liberty with leftwing oligarchy.”
The Justice Department operates independently of the president, and there is no evidence that President Biden has had any involvement in its prosecution decisions.
Mr. Trump wants to eliminate the department’s independence and has called for prosecuting his political opponents, purging federal agencies of civil servants who might oppose his policies and greatly expanding executive power.
Democrats expressed fear for the future of American democracy, as Justices Sonia Sotomayor, Elena Kagan and Ketanji Brown Jackson did in their dissenting opinion. “Simply frightening. May God have mercy on this nation,” Jaime Harrison, the chairman of the Democratic National Committee, wrote alongside Justice Sotomayor’s quote: “With fear for our democracy, I dissent.”
Mr. Biden’s deputy campaign manager, Quentin Fulks, said on a call with reporters that the Supreme Court had “handed Donald Trump the keys to a dictatorship.” Shortly before that, the Biden campaign put out a statement saying that the ruling did not change the facts of Mr. Trump’s actions leading up to and on Jan. 6, 2021: “Donald Trump snapped after he lost the 2020 election and encouraged a mob to overthrow the results of a free and fair election,” it said.
“Our democracy has been gravely wounded,” Eric H. Holder Jr., who served as attorney general under President Barack Obama, wrote in a post on social media, saying the Supreme Court had given presidents free rein to commit crimes. “There is no basis in the Constitution for this Court constructed monstrosity.”
Representative Alexandria Ocasio-Cortez of New York said the Supreme Court had been “consumed by a corruption crisis” and pledged to file articles of impeachment, though she did not specify against which justices. Justices Samuel A. Alito Jr. and Clarence Thomas have been under scrutiny because a flag associated with the “Stop the Steal” movement flew outside Justice Alito’s house after the 2020 election, and Justice Thomas’s wife was involved with efforts to overturn the election.
Supreme Court justices can be impeached, but only one has been — more than 200 years ago — and Republicans currently control the House.
Senator Chuck Schumer of New York, the Democratic leader, called Monday “a sad day for America” and added, “Treason or incitement of an insurrection should not be considered a core constitutional power afforded to a president.”
The district court judge overseeing Mr. Trump’s trial in Washington will have to determine whether his specific actions are protected under the ruling. That will take time and very likely delay a trial past the election — at which point, if Mr. Trump wins, he could order the Justice Department to end the case.
“I don’t see how this case could go forward before the election,” Alina Habba, a lawyer for Mr. Trump, said on Fox News.
Outside groups focused on democracy also condemned the ruling.
“The Court has issued an instruction manual for lawbreaking presidents,” said Michael Waldman, the president of the Brennan Center for Justice at New York University. “Make sure you conspire only with other government employees. You’ll never be held to account.”
Michael Gold, Simon J. Levien and Mattathias Schwartz contributed reporting.
