Even as details about what Trump may have offered Ukrainian President Volodymyr Zelensky in a July phone call remain sparse, battalions of lawyers are parsing Trump’s public statements and alleged actions to determine what laws he may have broken. But Trump’s lawyers point once more to a Justice Department opinion that presidents cannot be indicted.

Trump has said he did nothing wrong on the call. But the administration has refused to turn over to Congress details of the whistleblower complaint that brought the alleged offer to light. On Sunday, in a letter to lawmakers in both parties, House Speaker Nancy Pelosi (D-Calif.) accused the administration of “entering a grave new chapter of lawlessness.”

The president’s supporters argue — and many of Trump’s opponents concede — that conflicts such as this are more political than legal, and that the Ukraine matter doesn’t seem to have shifted public opinion or broken Washington’s stalemate any more than special counsel Robert S. Mueller III’s investigation of Russia’s role in the 2016 presidential election did.

“I don’t know that there’s anything more alarming here than what we see from this president 10 times a week,” said Andy Grewal, a law professor at the University of Iowa. He noted that “no president has ever been prosecuted for anything.”

Trump “tweets this stuff out all the time: ‘Investigate my enemies.’ I don’t see this moving the needle at all,” Grewal said. “If he’d just tweeted this out instead of making the call, we’d shrug and say, ‘More of the same.’ ”

A president who relishes provocation, an outsider who got elected in large part because he promised to disrupt and upend a system that relies on laws and regulations to curb excesses, Trump has throughout his life believed that laws are pesky obstacles that sometimes need to be pushed aside to get things done.

Starting with his first confrontation with federal prosecutors, in a 1973 case in which he and his father were accused of discriminating against black and Hispanic renters seeking apartments in their New York City developments, Trump has viewed the law as an impediment to profit and progress, Barbara Res, an early top executive in Trump’s real estate business, said in an interview earlier this year.

“He ignores the law when he doesn’t like it, he uses the law to get his way,” Res said. “He sees it as a weapon to use to get what he wants.”

Now, almost half a century later after his first legal battle, Trump’s time as president is confronting the nation with a basic question about the American political system: Does this president’s skepticism about the law and improvisational method of governing confound the checks the Constitution provided to rein in a president’s power?

If a crime was committed in the Ukraine matter, legal scholars say, it may have been a violation of laws that prohibit bribery, bar Americans from seeking to influence foreign officials and ban foreign involvement in U.S. election campaigns.

Because the law defines bribery as the giving or taking of a thing of value for the purpose of influencing an official’s actions, “the issue would be whether the promise to investigate [Biden’s son] Hunter Biden was a thing of value that was offered and accepted,” Grewal said. “Some people will say it’s an intangible with no obvious value, and others will say it’s evidently a thing of value to kneecap your opponent.”

Trump’s apparent acknowledgment Sunday that he discussed Hunter Biden’s work in Ukraine with the Ukrainian president has spurred a new wave of allegations that Trump crossed a line in that phone call. But legal experts said that although the conversation may have been politically inappropriate, it’s not clear that such a discussion would violate bribery laws because a thing of value may not have been offered or accepted.

The Mueller report got hung up on what exactly constitutes a thing of value, concluding in its discussion of a Trump Tower meeting between Trump campaign officials and a Kremlin-connected Russian lawyer that, as Grewal summarized it, “it was debatable whether the dirt on [Democratic opponent] Hillary Clinton was a thing of value.”

But in that instance, “Trump wasn’t yet the president,” said Washington lawyer Eric L. Lewis, a partner at Lewis Baach who specializes in international fraud and corruption cases. “He just said, ‘Russia, if you’re listening, dig up some dirt on the Clinton emails.’ In this case, the question is: Is investigating your opponent and thereby increasing your chances to win the election a thing of value? People have gone to jail for less.”

Lewis said any promise Trump may have made to the Ukrainian president could be investigated as a “breach of the Foreign Corrupt Practices Act. He’s a U.S. person offering something to a foreign person for personal advantage, and that’s what the law prohibits.”

But whatever laws may be involved in any inquiry into Trump’s actions, the fact that prosecutors would not file charges against a sitting president makes this more a political question than a legal one.

“The framers were unwise to give the president such a huge amount of power in foreign affairs,” Lewis said, “but they were wise to have a remedy in the legislative branch” — Congress’s ability to impeach and remove a president who criminally abuses power.

Some scholars say the U.S. political system has demonstrated its effectiveness already in this case because an unnamed intelligence official felt confident enough in the federal protections for whistleblowers to raise the alarm about Trump’s alleged promise.

“In one sense, the system has already worked here because we know about the call thanks to the whistleblower statute,” Grewal said.

The call and Trump’s alleged promise have unleashed a torrent of outrage from Democrats and anti-Trump Republicans arguing that the president’s disregard for the rules of the road is unprecedented.

“Putting the impeachment question aside, the national security implications of a President asking a foreign power to investigate an American citizen for the president’s own political benefit [are] unprecedented,” tweeted Kelly Magsamen, a Pentagon official in the Obama administration and now vice president for national security at the Center for American Progress, a left-leaning Washington think tank. “And it can induce other foreign powers to do similar to curry favor.”

But in some ways, the country has been here before.

“When the president does it, that means it’s not illegal,” Richard Nixon said in a 1977 interview, three years after President Gerald Ford pardoned him for any crimes he might have committed as president.

Nixon went on to say that a president’s power is not completely unchecked, but that the only really effective guardrail the system provides is the next election. “So that one does not get the impression that a president can run amok in this country and get away with it,” he said, “we have to have in mind that a president has to come up before the electorate.”

Nixon resigned from the presidency as his popular support collapsed and at the cusp of what appeared to be certain impeachment by the House and likely conviction by the Senate. “I have impeached myself,” Nixon would say later.

Former White House counsel John Dean. (Marvin Joseph/The Washington Post)

Earlier this summer, when Nixon’s White House counsel, John Dean, appeared before the House Judiciary Committee to talk about the Mueller investigation, he warned that “history is repeating itself, and with a vengeance.”

But Trump at this point faces none of the threats that Nixon ran up against in his final months in office. Trump’s support in opinion polls has remained rock-steady, although always short of majority approval, and his Republican support in Congress is still nearly monolithic.

“He thinks he’s invincible, and he’s probably right,” Lewis said.

In his 1977 interview with David Frost, Nixon maintained that “technically, I did not commit a crime, an impeachable offense,” but he also conceded that “these are legalisms.”

“I let down the country,” he said. “I let down our system of government and the dreams of all those young people that ought to get into government but will think it is all too corrupt.”

When Nixon resigned, Trump was a young man making his way into the Manhattan real estate business. Trump told The Washington Post’s Bob Woodward and Robert Costa in 2016 that Nixon was a “great talent” who “failed . . . because of his personality. Very severe, very exclusive.”

Trump has dismissed comparisons of his presidency with Nixon’s.