Local and national leaders pushed back Wednesday against President Trump’s desire to deliver his convention acceptance speech from the White House, warning that the event could bring protests and novel coronavirus spread to the nation’s capital while violating historic norms that separate political activity from the seat of presidential power.

House Speaker Nancy Pelosi (D-Calif.) predicted that a political convention gathering at the White House “won’t happen,” for legal and ethical reasons, while D.C. Mayor Muriel E. Bowser (D) said she did not plan to offer “any exemptions” for the event from a recent health order that restricts the movement of nonessential visitors to the city from 27 states with elevated rates of the virus.

Members of the D.C. Council expressed alarm about the idea, and on Capitol Hill, some Republicans also voiced concern. Sen. John Cornyn of Texas called it “problematic,” Sen. John Thune (S.D.) questioned the legality of political events at the White House and Sen. Ron Johnson (Wis.) suggested that other plans should be made.

“Probably not allowed,” he said. “Probably shouldn’t do it.”

The pushback came as Trump indicated publicly for the first time that he preferred speaking from the White House at the end of four nights of convention programming, from Aug. 24-27, that will be a mix of live speeches from around the country and prerecorded video. In an interview Wednesday on “Fox & Friends,” he described the White House as a “beautiful setting” that is “greatly representative of our nation” where the logistics would be easy and inexpensive to arrange.

A Republican involved in the planning said it was highly likely that Trump’s speech would be delivered at the White House, perhaps on the South Lawn, but various locations were being discussed. Vice President Pence was considering Fort McHenry in Maryland, the site of a major battle in the War of 1812, to give his convention speech.

This official said Republicans were not concerned about the ethics of staging convention events at the White House and thought the American public would understand, particularly because the president’s travel options are limited by the pandemic. Republicans already have moved the convention celebrations from both Jacksonville, Fla., and Charlotte.

“I will probably do mine live from the White House,” Trump said Wednesday morning. “If for some reason somebody had difficulty with it, I could go with someplace else.”

When asked about Republican concerns over the legality of using the White House for a political event, Trump was dismissive. “It is legal,” he said during a Wednesday evening news conference.

Trump has traveled to several key November states in recent months to hold rallies and fundraisers, but former vice president Joe Biden, the presumptive Democratic nominee, has limited his campaign activities to occasional policy speeches near his Delaware home, a visit to Washington to meet with former president Barack Obama, and regular virtual events.

Democrats on Wednesday announced that Biden had canceled his plans to travel to Milwaukee for the convention because of the virus. Instead, he will address the nation from his home in Wilmington, Del., on Aug. 20 with the rest of the Democratic convention occurring virtually from locations around the country beginning Aug. 17.

Unlike other cities, D.C. has little power to prevent presidential events from taking place on federal land, with protection provided through a combination of local police and federal officials.

When the Trump administration moved forward with plans to hold Independence Day festivities on the Mall, city officials urged people not to attend and to celebrate at home. But the mayor was powerless to stop an event on federal property and did not take formal steps to curb attendance, such as when she ordered the closure of city streets near the Tidal Basin when the cherry blossoms drew crowds.

That has not stopped members of the D.C. Council from speaking out. “My first priority is to ensure the health and safety of District residents,” D.C. Council member Brooke Pinto (D-Ward 2), whose district includes downtown, said in a statement Wednesday. “I do not believe that hosting the Republican National Convention in DC will help us to meet that goal.”

D.C. Council member Mary M. Cheh (D-Ward 3) said Wednesday that the events could stir up protests against Trump and police brutality that filled streets near the White House in June.

“It could be a lightning rod for confrontation,” she said.

One obstacle for Republican planners are current health orders in D.C. that require anyone who comes to the city for a nonessential reason from coronavirus hot spots to self-quarantine in a hotel room, house or apartment for 14 days, venturing out only for essentials such as groceries or medical treatment. Those hot spots include many states important to Trump’s reelection, including Florida and Wisconsin, potentially restricting who could attend his convention events.

That timeline would, for the affected convention attendees, begin early next week, but it was not clear whether delegates from those states planned to attend. District rules limit public gatherings to 50 people.

“If they comply with the law, they are more than welcome to come to Washington,” Cheh said. “Otherwise, they should stay home.”

Under the mayor’s order, government employees, including the president, are exempted from the quarantine rules and are allowed to move around as soon as they arrive in D.C., as long as they monitor themselves for symptoms.

Republican officials have noted that Bowser has not been actively enforcing her order by seeking out those who break it. Under local law, anyone who “willfully violates” the order can be charged with a misdemeanor, fined up to $1,000 and imprisoned for up to 30 days, though no charges have yet been filed.

A D.C. police spokeswoman would not answer specific questions about convention events but said officers are focused on education rather than fines or arrests while enforcing the mayor’s orders.

“MPD continues to do our part to help stop the spread of covid-19 in our city by encouraging and educating the public on wearing masks and adhering to the Mayor’s orders,” the spokeswoman said. “Voluntary compliance is our desired goal.”

In a news briefing on Wednesday, Bowser said she had not had any conversations about planning for Republican convention activity.

“I don’t know we anticipate any exemptions for the quarantine until we lift the quarantine,” she said.

Civil rights leaders are planning a march in Washington that could draw thousands to the city on Aug. 28, one day after Trump plans to deliver his acceptance speech. The Rev. Al Sharpton, who is organizing the march, said he has been working with Bowser’s office to ensure that the event does not violate local rules. He said people from the states listed in the mayor’s quarantine order are being told to stay home, and no buses carrying protesters will travel from those locations.

“We want to make sure that this is ultrasafe,” Sharpton said. “We will not let anyone in without taking their temperature both on the buses and the march.”

Trump would also have to overcome legal and ethical obstacles that have historically kept the White House from being used for political events.

“You don’t have political events at the White House,” Pelosi said in an interview Wednesday on MSNBC. “You can’t do it.”

An adviser to the speaker said Pelosi was concerned that a convention event at the White House could lead to the misuse of congressionally appropriated funds or violate the Hatch Act, which prevents most federal officials from participating in political activity at work.

The Hatch Act exempts both the president and the vice president from restrictions and does not apply to “rooms in the White House or in the residence of the Vice President, which are part of the residence area or which are not regularly used solely in the discharge of official duties.” Hatch Act violations are investigated by the Office of Special Counsel, which refers its findings back to the White House to take further action.

But holding a convention event at the White House could still raise complications for any lower-ranking White House officials who participate during work hours. Richard Painter, a Trump critic who served as chief White House ethics lawyer under President George W. Bush, said the challenge of staging a convention from the White House is not that Trump himself would be violating the law.

“He may not be violating the Hatch Act, but he is ordering other people to,” Painter said. “At a certain point you are using White House resources, and that is a violation of the Hatch Act.”

Two Democratic lawyers, who spoke on the condition of anonymity to discuss private deliberations, said that while Hatch Act violations do not result in criminal prosecutions, the misuse of congressionally appropriated funds for a political purpose could be criminally enforceable. The statute of limitations would not have run out in 2021, when the winner of this year’s election takes office.

Republican planners have discussed seeking a way to reimburse the federal government for any expenses incurred at the White House or on other federal property for the convention, though it is not clear how the value would be estimated.

“The RNC would have a difficult time arguing that they can reimburse for the expenses, because how do you calculate such things as the fair market value of the White House lawn?” said Kedric L. Payne, the senior director of ethics at the Campaign Legal Center.

Other Republicans on Capitol Hill were more supportive of Trump’s desire to use the White House for convention events, given the pandemic-related restrictions.

“Well, he lives there,” Sen. Mike Rounds of South Dakota said. “What are his options?”

Even Sen. Mitt Romney (Utah), a regular Trump critic, expressed some sympathy for the president’s plight. “I don’t know whether it is technically legal or not,” he said, “but it has got to be [held] somewhere.”

National Democrats, meanwhile, signaled that they would try to use Trump’s decision to pursue a White House political event as another example of his norm-breaking presidency.

“It’s epically breathtaking to hear the president say that — ‘I’m going to give a political speech from the White House,’ ” Democratic Party Chairman Tom Perez said on MSNBC. “That would be a nonstarter for any Democrat running. That is so unethical.”

Karoun Demirjian and Peter Hermann contributed to this report.