WASHINGTON — President Donald Trump’s announcement on Thursday that he is giving a full pardon to conservative provocateur Dinesh D’Souza while at the same time considering clemency for Martha Stewart and imprisoned former Illinois Gov. Rod Blagojevich, has underscored the relish he takes in that power — in ways that break norms dating to the nation’s start.

The D’Souza pardon would be Trump’s fifth, and the latest in a pattern of using the president’s near-absolute authority to benefit individuals in legal trouble based on his political whim or convenience.

Trump’s critics suggested the pardons could amount to a signal from the president to associates implicated in the Russia probe that he would consider pardoning them. Among the critics Thursday was Sen. Mark Warner of Virginia, the senior Democrat on the Senate intelligence committee, which is investigating Russia’s election interference and possible Trump campaign cooperation.

“The President’s ad hoc use of the pardon power is concerning enough,” Warner wrote on Twitter. “But the possibility that he may also be sending a message to witnesses in a criminal investigation into his campaign is extremely dangerous. In the United States of America, no one is above the law.”

The pardon power under Article II of the Constitution is one of a president’s most absolute. That has made it particularly appealing to Trump, given his penchant for decisive acts and his evident frustration with the checks and balances that, for most actions, require a president to share power with Congress and the federal courts — and potentially be blocked by those other two branches of government.

Since George Washington, however, presidents have, for the most part, voluntarily accepted restraints on their ability to pardon. Starting in 1789, government lawyers have been designated to review pardon applications. And since 1865, presidents have typically relied on a review by the Justice Department before granting clemency.

Trump has seemed to act on impulse or the urgings of friends and celebrities in making his clemency decisions. Three of his five pardons have gone to people backed by his conservative political allies — D’Souza, Lewis “Scooter” Libby and Joe Arpaio, the former Maricopa County, Ariz., sheriff.

Film star Sylvester Stallone lobbied Trump to pardon Jack Johnson, the late African-American boxer, who was convicted in 1920 on charges stemming from his sexual relations with a white woman.

The White House would not say who urged Trump to pardon D’Souza, but gaining clemency for him has been a cause for Trump’s confidant Sean Hannity, the Fox News host, and Sen. Ted Cruz of Texas, who say D’Souza was targeted for his caustic, sometimes racist, criticism of President Barack Obama and his wife.

Another pattern is that Trump has seemed to favor clemency for people prosecuted by his nemeses: D’Souza was prosecuted by Preet Bharara, who Trump fired as U.S. attorney in Manhattan. Stewart’s prosecution was directed by one of Bharara’s predecessors in that job, James Comey, who Trump later fired from his job as FBI director.

Blagojevich’s prosecutor was Patrick Fitzgerald, a friend of Comey’s who also prosecuted Libby, the former aide to Vice President Dick Cheney who Trump pardoned in April. Libby was convicted in 2007 of perjury and obstruction of justice.

For Trump, the day’s pardon action began early Thursday, when he tweeted: “Will be giving a Full Pardon to Dinesh D’Souza today. He was treated very unfairly by our government!”

D’Souza pleaded guilty in 2014 to campaign finance fraud.

Trump did not explain how D’Souza had been treated unfairly, but the White House, in a statement, said that “D’Souza was, in the President’s opinion, a victim of selective prosecution for violations of campaign finance laws.”

The federal judge in the case decided otherwise in 2014 when D’Souza raised that claim in court, saying D’Souza had “no evidence” for his contention.

Stewart, the lifestyle entrepreneur, was convicted in an insider trading case in 2004.

Trump said of Stewart: “She used to be my biggest fan in the world … before I became a politician.”

Blagojevich, a Democrat, was impeached and removed from office, and convicted in 2011 of corruption, for seeking to benefit from making a Senate appointment to fill the vacancy after Obama became president.

Blagojevich was a contestant on “Celebrity Apprentice” in 2010.

jackie.calmes@latimes.com