In Legal Peril, Trump Tries to Shift the Spotlight to Biden

But he said members of outside Democratic groups would most likely begin coming to Mr. Biden’s defense if the attacks continued.

“This is such a charged and hot subject,” Mr. Vale said. “There’s nothing to be gained by weighing in. But I think as it goes on, you will have folks on the outer circle weighing in.”

Strategists for Mr. Trump promise that the attacks will continue.

Chris LaCivita, a senior campaign consultant for Mr. Trump, said on Wednesday that it was fair to assign responsibility for the investigation to Mr. Biden because the special counsel was appointed by Mr. Biden’s attorney general.

“There’s a thing called in government, the chain of command,” he said.

America First Legal, the pro-Trump group founded by Stephen Miller, the architect of the former president’s immigration agenda, sent out a fund-raising appeal on Wednesday morning, using the indictment as a rallying cry.

The theme has been echoed by Mr. Trump’s staunchest allies in Congress, who trained their ire on Mr. Biden even as they also railed against the Justice Department, the F.B.I., the “mainstream media” and Democrats generally.

Most of them, it seemed, were trying to goad Mr. Biden into a reaction.

“I, and every American who believes in the rule of law, stand with President Trump against this grave injustice,” tweeted Speaker Kevin McCarthy, the leading Republican in Congress.

Mr. Biden has so far focused on governing.

On Tuesday, the president met with Jens Stoltenberg, the secretary general of NATO, in the Oval Office. Later, he hosted a Juneteenth concert on the South Lawn of the White House, an event where it was easy to avoid the subject of Mr. Trump.