By Matthew Rusling

WASHINGTON, May 23 (Xinhua) -- U.S. President Donald Trump is on a dangerous path in his open battle with the U.S. Justice Department, which experts bill as a bad sign for the future of U.S. democracy.

"No president has challenged the rule of law in such a fundamental manner. That is ominous for the future of American democracy," Brookings Institution Senior Fellow Darrell West told Xinhua.

"Others such as Nixon have complained about law enforcement, but not seriously undermined its ability to do its job. Trump has gone beyond talk to real-live demands," West said, referring to the investigation that led to former president Richard Nixon's resignation in 1974.

Indeed, this month marked the one-year anniversary of the ongoing probe by special counsel Robert Mueller on whether Team Trump colluded with Russia to clinch the White House in the 2016 presidential elections, and the latest shot in the open battle between the White House and the president's own Justice Department came earlier this week.

That's when Trump demanded in a Tweet that the Justice Department investigate whether they or the FBI surveilled his campaign at the behest of the Obama administration in the lead up to the 2016 presidential elections.

"I hereby demand...that the Department of Justice look into whether or not the FBI/DOJ infiltrated or surveilled the Trump Campaign for Political Purposes -- and if any such demands or requests were made by people within the Obama Administration!" the president tweeted Sunday.

"This is a very dangerous game -- Trump is undercutting a lot of norms of presidential behavior here," Christopher Galdieri, assistant professor at Saint Anselm College, told Xinhua.

"He's creating an impression that federal law enforcement is motivated by political concerns, not the pursuit of justice. He's also potentially laying the groundwork for himself to use the FBI and DOJ for political ends -- if he convinces his supporters that that's just what presidents do, then they, at least, would support any efforts on his part to do the same," Galdieri said.

"And thanks to political polarization, there are millions of Americans who support Trump and are now convinced that the FBI and DOJ are not professional law enforcement agencies, but left-wing cabals trying to bring down Trump and his administration," Galdieri said.

West said that by calling for an investigation of the FBI, Trump is endangering democratic norms and "setting the precedent that chief executives can investigate the investigators."

"That would imperil the FBI and make it impossible to launch future investigations for fear they would be politically attacked. Trump's demand sets a very risky precedent for later administrations. In the wrong hands, it could be completely abused and enable chief executives to do anything without any legal risk," West said.

Dan Mahaffee, senior vice president and director of policy at the Center for the Study of Congress and the Presidency, expressed concern that many Republicans in Congress are willing to join with Trump's attack on these institutions in a bid to protect Trump and his administration.

"For democracy, there must be the independent application of the law and investigations, counterintelligence, and law enforcement must be depoliticized," Mahaffee said.