In a statement this week, Mr. Wheeler, a Democrat, said he feared the arrival of Saturday’s demonstrators more than the ongoing demonstrations against racial injustice in his city.
“I categorically condemn violence of all kinds by all people,” Mr. Wheeler said in a statement. “But let me be clear, the alt-right and white supremacist groups organizing to come to Portland on Saturday present the greatest threat we’ve faced so far.”
On Friday, Alan Swinney, one of the far-right activists involved in clashes this summer in Portland, said he had been indicted and planned to turn himself in. It wasn’t immediately clear what charges he faced.
Portland has a long history of left-wing activists organizing to confront white supremacists or other far-right groups. Some incidents occurred as the city’s progressive organizers tried to quash some of the most explicit remnants of the region’s troubled racial history, which included Oregon’s status as the only non-slavery state to join the union with a constitutional clause that excluded Black people.
In the Trump era, a variety of right-wing groups, including the Proud Boys, have organized events in the city, some with the explicit intention of spurring confrontations with local activists. Leftists, including those who are part of the collective Rose City Antifa, one of the more prominent and organized antifa groups, have gathered to oppose them.
“The anti-fascist position has always been: never let fascists control the streets,” said Joseph Lowndes, a professor of political science at the University of Oregon who researches right-wing political trends. Mr. Lowndes said that while events that draw groups like the Proud Boys often lead to violence, he worried that recent events in Portland — including an antifa supporter’s killing in August of Aaron J. Danielson, an activist with the far-right group Patriot Prayer — raises the prospect of even more confrontation.
Giulia McDonnell Nieto del Rio contributed reporting.