WASHINGTON (AP) — The Trump administration has deployed agents with tactical gear to confront protesters in downtown Portland, Oregon. That has sparked debate over the use of federal power as local and state officials, and many in the community, condemn their tactics and demand they leave. Far from backing down, the administration plans to send agents to Chicago to respond to gun violence. And President Donald Trump says federal agents could be deployed elsewhere as he makes law and order a central element in his struggling re-election campaign.

A look at some of the issues behind this unconventional, if not unprecedented, use of federal forces:

WHAT'S BEEN GOING ON IN PORTLAND?

Protests over the killing of George Floyd by police in Minneapolis have taken place in downtown Portland for more than 50 consecutive days, drawing at times more than 10,000 mostly peaceful demonstrators. A relatively small number of activists have vandalized downtown buildings, including the federal courthouse. Trump issued an executive order June 26 to protect monuments and federal property after protesters tried to remove or destroy statues of people considered racist, including a failed attempt to pull down one of Andrew Jackson near the White House. The Department of Homeland Security then created a task force to protect federal property and dispatched agents to Portland as well as Seattle and Washington, D.C., starting around the Fourth of July weekend.

WHY THE DEPARTMENT OF HOMELAND SECURITY?

DHS, which was formed after the Sept. 11, 2001, attacks to improve the nation's response to the threat of international terrorism, oversees some of the largest U.S. law enforcement agencies. That includes the Border Patrol as well as Immigration Customs and Enforcement, which are seeing less of their usual activity because of COVID-19. DHS also oversees the Federal Protective Service, which guards federal buildings along with the U.S. Marshals Service. DHS sent members of the Border Patrol, along with Secret Service officers, Air Marshals and others, to Portland to protect the downtown courthouse complex.

WHAT HAPPENED AFTER FEDERAL FORCES ARRIVED?

Federal officers and protesters clashed in the streets outside the federal courthouse. Demonstrators broke windows and did other damage, hurled rocks at the officers and shined lasers in their eyes. Agents fired tear gas to disperse demonstrators and arrested about a half-dozen people, mostly for minor offenses, and issued citations. Tensions escalated after an officer with the Marshals Service fired a less-lethal round at a protester's head on July 11, critically injuring him. They ratcheted up further when agents in unmarked vehicles with generic "police" patches on their camouflage uniforms arrested people at night without identifying themselves. The government said it was done to protect officers from violent crowds, but it felt to many like the U.S. had created a secret police force, and it drew lawsuits as well as more protesters into the streets.

IS IT LEGAL FOR FEDERAL FORCES TO BE USED LIKE THIS?

Yes, to a certain extent. Federal authorities can enforce federal laws on federal property, like the courthouse in downtown Portland. But state and local officials have not authorized the federal government to operate outside their jurisdiction, and that has raised constitutional issues now being challenged in court. As Michael Dorf, a professional of constitutional law at Cornell University, told The Associated Press, "The idea that there's a threat to a federal courthouse and the federal authorities are going to swoop in and do whatever they want to do without any cooperation and coordination with state and local authorities is extraordinary outside the context of a civil war."

EVEN IF IT'S LEGAL, IS IT A GOOD IDEA?

DHS has assisted with local enforcement before, but not without consent. It sent agents to Puerto Rico to help confront a spike in crime linked to drug trafficking in 2013 and dispatched the Border Patrol's tactical team to track two escaped convicts in rural upstate New York in 2015. But as John Cohen, a former senior DHS official under Obama and President George W. Bush, noted, those were conducted in close cooperation with state and local authorities. Employing DHS on its own, in a mission that seems to be suspiciously aligned with the president's reelection campaign, appears to be unprecedented. "If the public begins to perceive that they are being partisan in how they operate they lose credibility, and if they lose credibility, they lose public trust," said Cohen, who now teaches at Georgetown University.

WHAT CAN BE EXPECTED TO HAPPEN NEXT?

The Oregon attorney general filed a lawsuit Friday arguing that the federal government had violated the rights of citizens of the state by detaining people without probable cause. The American Civil Liberties Union has also sued, seeking to stop the federal government's use of rubber bullets, tear gas and acoustic weapons against journalists and other legal observers. These and other legal actions could force the federal agents to change tactics or perhaps downsize their mission in the city. But the actions of DHS seemed to have pleased Trump. He has praised acting DHS Secretary Chad Wolf and criticized local officials for letting a situation get "out of control." An official told the AP that Homeland Security was planning to deploy about 150 agents to Chicago for at least two months in a mission expected to focus on gun crime, not the protection of federal property. Trump, who sees the use of federal officers as a way to embarrass Democratic local officials, wants them used in other cities. "We're going to have more federal law enforcement, that I can tell you," Trump said Monday.

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Associated Press writers Gillian Flaccus in Portland, Ore., and Colleen Long in Washington contributed to this report.