In a recurring point of interest for the court as it questioned the government, Justice Brett Kavanaugh raised the question of the "risk" of a "creative prosecutor" using "vague" criminal statutes -- including obstruction and conspiracy, which Trump faces -- against any president if they can't claim immunity.

In response, Department of Justice attorney Michael Dreeben said the question about the risk is "very serious" and "obviously it is a question that this court has to evaluate." He argued there is a "balanced protection" with "accountability" for the presidency.

Both Kavanaugh and Justice Samuel Alito appeared skeptical of Smith's use of at least some of the conspiracy and fraud-related charges in the case against Trump. Alito said to Dreeben: "I don't want to dispute the particular application of that [conspiracy statute] to the particular facts here, but would you not agree that is a peculiarly open-ended statutory prohibition? And that fraud under that provision, unlike under most other fraud provisions, does not have to do -- doesn't require any impairment of a property interest?"

Dreeben responded: "It is designed to protect the functions of the United States government and it is difficult to think of a more critical function than the certification of who won the election."

Justice John Roberts began his line of questioning by raising concerns about the opinion issued by the D.C. Circuit Court of Appeals in their rejection of Trump's claims of immunity.

Roberts said the statement that "a former president can be prosecuted for his official acts because the fact of the prosecution means that the former president has allegedly acted in defiance of the laws" concerned him because "as I read it, it says a former president can be prosecuted because he's being prosecuted."

Roberts said such a position could put too much faith in the justice system to act non-politically and out of good faith, and he asked whether the Supreme Court should send the opinion back down to make clear to the circuit court that that is not the law.

Michael Dreeben, arguing for the government, responded that there are "layered safeguards" that protect against malicious prosecution.

"We are not endorsing a regime that we think would expose former presidents to criminal prosecution in bad faith, for political animus, without adequate evidence or politically driven prosecution that would violate the Constitution," Dreeben said.

Asked by Justice Clarence Thomas why previous presidents were not prosecuted for controversial actions, prosecutor Michael Dreeben said "this is a central question."

"The reason why there have not been prior criminal prosecutions is that there were not crimes," he said.

He said there are "layers of safeguards" that ensure that former presidents do not have to "lightly assume criminal liability for any of their official acts."

After about an hour of questioning, Trump's attorney concluded his presentation before the court and Department of Justice attorney Michael Dreeben, representing Smith's team, began his argument with a short opening statement followed by what is expected to be approximately an hour of facing questions.

Dreeben called Trump's immunity claim a "novel theory [that] would immunize former presidents for criminal liability for bribery, treason, sedition, murder and, here, conspiring to use fraud to overturn the results of an election and perpetuate himself in power."

"Such presidential immunity has no foundation in the Constitution," Dreeben said. "The framers knew too well the dangers of a king who could do no wrong."

-ABC News' Adam Carlson

Justice Samuel Alito has multiple times over the course of questioning sounded sympathetic toward Trump's positions.

He also seemed to raise concerns about former presidents suffering the burden of having to go through a trial if they are criminally charged.

"That may involve great expense, and it may take up a lot of time, and during the trial the former president may be unable to engage in other activities that the former president would want to engage in, and then the outcome is dependent on the jury, the instructions to the jury and how the jury returns a verdict, and then it has to be taken up on appeal," Alito said at one point.

In his final question to government attorney Michael Dreeben, Alito seemed to suggest that Trump's prosecution could serve to incentivize future presidents to try and unlawfully remain in office in order to avoid prosecution by their successors.

"Now, if an incumbent who loses a close, hotly contested election knows that a real possibility after leaving office is not that the president is going to be able to go off into a peaceful retirement -- but that the president may be criminally prosecuted by a bitter political opponent. Will that not lead us into a cycle that destabilizes the functioning of our country as a democracy?" Alito asked.

"I think it is exactly the opposite, Justice Alito," Dreeben replied, noting Trump and his allies filed dozens of lawful challenges to the results of the election and lost.

"There is an appropriate way to challenge things through the courts with evidence," Dreeben said. "If you lose, you accept the results, that has been the nation's experience, I think the court is well familiar with that."