Washington (CNN) There are multiple explanations for President Donald Trump's latest pardon storm but they are all rooted in a defining character trait -- his relish for wielding unchecked power.

By expunging the conviction of conservative filmmaker Dinesh D'Souza, and by hinting at more controversial pardons to come, Trump is showing his willingness to test the limits of his power and to crush the conventions and unwritten restraints surrounding the Oval Office.

Critics are protesting that his move reveals political shallowness, subverts the justice system and sends a message to aides under duress from special counsel Robert Mueller.

But Trump seems to be saying,"I have this power, so why not use it?"

The President's D'Souza pardon, and possible pardon for Martha Stewart and commutation for Rod Blagojevich , is not part of a larger strategy to send a signal to Mueller and fired FBI Director James Comey, a senior White House official told CNN's Pamela Brown.

The official said that often people will bring up potential pardons to the President's attention and then he'll start floating the idea internally. The official added, though, that Trump naming Stewart and Blagojevich came as a surprise to staffers.

The question is not whether Trump did anything wrong legally, but whether his use of this supreme authority is timely and appropriate.

The first thing to note is that he is acting in line with Article II of the Constitution, which gives the President power to "grant reprieves and pardons for offenses against the United States, except in cases of impeachment."

That authority represents one of the most unfettered powers granted to the commander in chief -- one reason why presidents have often been careful in its use, frequently waiting until the dying hours of their administrations to grant their most contentious pardons.

Trump has not shown much interest in the idea that the office of the presidency itself is sacred and in need of protection. And he seems perfectly OK using its trappings as a vessel for advancing personal or political interests.

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Unchecked power?

The D'Souza pardon adds to growing questions, including Trump's attacks on the Justice Department and the FBI, about the President's willingness to submit to checks on his own authority.

"I think the President is beyond just messaging -- I think he is testing the boundaries of the presidency," Carrie Cordero, a former counsel to the assistant attorney general for national security, told CNN's Wolf Blitzer.

"I think he is trying to use the presidency, potentially in ways that we have not seen in modern times," Cordero said, noting that most other presidents since the end of the 19th century used the Justice Department to review pardon decisions.

A Justice Department spokesman told CNN Thursday that Trump did not run the pardon through the agency's Office of the Pardon Attorney, as was also the case for the controversial pardons of Dick Cheney's former chief of staff I. Lewis "Scooter" Libby and former Arizona Sheriff Joe Arpaio.

"What this President has done, which we have not seen in centuries, literally, is the President making unilateral decisions ... absolutely 100% bypassing any of that policy process. I think he is looking for ways to expand his presidency and he is seeing how far the other branches of government are going to let him get away with it," said Cordero.

Corey Brettschneider, a constitutional law professor at Brown University and Fordham Law School, said pardon power is meant to be a merciful gesture to those who have suffered at the hands of the law.

"Part of the idea of mercy is showing regard for others rather than self-interest," he said. "The worry is that these pardons are not about that -- they are about the President's own ambitions and own desire to show his own power and his desire not to be subservient to laws or constitutional ideas.

"I worry that it is a kind of threat gesture and he is going to use the powers to the presidency as far as he is going to take them," added Brettschneider, author of the forthcoming book "The Oath and the Office."

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Motivations

Trump has many political, legal and personal motivations for wielding his power to pardon D'Souza, who pleaded guilty to violating campaign finance laws in 2014 after being indicted on charges of illegally using straw donors to contribute to a Republican Senate candidate.

The President explained on Twitter that D'Souza had been "treated very unfairly" by the government.

But by pardoning a vehement pro-Trump agitator, the President made a clear statement that if other supporters who are wildly popular with his base stick with him, he will protect them.

That dynamic was clearly at play when Trump caused a storm last year by pardoning Arpaio after he was convicted of criminal contempt in a case relating to his hardline policies towards undocumented immigrants.

Arpaio was a vocal proponent of Trump's 2016 campaign and used his national notoriety to advocate for Trump's similarly aggressive stance on border security and deportations.

His reprieve outraged civil rights groups and some Republican critics of the President, such as Sen. John McCain, who said the move undermined respect for the rule of law because Arpaio had shown no remorse for his actions.

Trump's decision to use his power to pardon D'Souza similarly worried electoral reform advocates because at the time of his sentencing he admitted he knew he was breaking the law by using straw donors.

"Donald Trump has sent a message to his friends and cronies that if you break laws to protect him or attack our democracy, he's got your back," said David Donnelly, president and CEO of Every Voice, a money-in-politics watchdog group.

White House deputy press secretary Raj Shah, however, said that D'Souza had made restitution and accepted responsibility for his actions.

But Shah, speaking on Fox News, also hinted at a partisan motive, by saying that the conservative hero was the subject of "selective prosecution" by the Obama administration.

And in a comment that could start alarm bells ringing -- he said that D'Souza was convicted of "infractions and crimes" that are rarely prosecuted.

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Future implications

It's not impossible that a similar rationale could be used should Trump's personal attorney Michael Cohen be found guilty of infringing campaign finance laws with a hush payment to adult film star Stormy Daniels. So far Cohen has not been charged with any wrongdoing, but his office and residences were raided by the FBI in April.

There's another reason why Trump's decision to use his pardon power again on such a politically sensitive case will cause concern: It could be interpreted as a signal to Cohen and other Trump acolytes -- such as indicted former campaign chairman Paul Manafort -- that if they don't play ball with prosecutors, they can expect a reward.

Rep. Steve Cohen, D-Tennessee, told CNN Thursday that a GOP colleague had told him to expect more signaling pardons from the White House.

"What he was saying, basically, was we are going to have a Saturday Night Massacre, when there is going to be several pardons in one day. I think Manafort knows it. I think Michael Cohen knows it. I think Robert Mueller probably knows it," Cohen said.

The idea that Trump could pardon someone who has been treated "very unfairly" by the government could serve in future as a blanket get-out-of-jail card for anyone in his campaign, or even his family who needs a pardon, should Mueller secure convictions.

Trump has also shown he is willing to use the muscle of his office to satisfy personal grudges.

That's one reason why his comment to reporters Thursday that he was thinking of pardoning jailed former Illinois Gov. Rod Blagojevich, a Democrat, and design guru Martha Stewart, who said she voted for Hillary Clinton.

Stewart was prosecuted by Trump's nemesis James Comey when the former FBI director was US attorney for the Southern District of New York. Blagojevich was sent down for political corruption by one of Comey's best friends -- Chicago prosecutor Patrick Fitzgerald. And Fitzgerald was also behind the conviction of Libby.

It could all be a massive coincidence, of course.

A senior White House official told CNN's Brown on Thursday that it was doubtful that Trump even knew about the involvement of the former FBI director and his circle in the convictions.

But he's surely relishing the notion that he could use presidential power to gut the legal legacy of a political enemy -- Comey -- just as he is doing in a political sense with former President Barack Obama.