Although some G.O.P. lawmakers see the appointment of David C. Weiss as a vindication of their strategy, others criticize the now-scuttled plea deal he struck with Mr. Biden.

Congressional Republicans have for months repeatedly written to Attorney General Merrick B. Garland demanding he appoint a special counsel to investigate Hunter Biden, the president’s son, over his business dealings.

Some even demanded that a specific man be named to lead the inquiry: David C. Weiss, the Trump-appointed Delaware U.S. attorney who has long investigated the case.

But on Friday, after Mr. Garland elevated Mr. Weiss to special counsel status, Republicans in Congress reacted publicly not with triumph, but with outrage. “David Weiss can’t be trusted and this is just a new way to whitewash the Biden family’s corruption,” Republicans on the House Judiciary Committee wrote on X, the social media platform formerly known as Twitter.

The reaction was a notable political development, one that underscored both how Mr. Weiss, a Republican, has fallen in conservative circles, and how deeply it has become ingrained in the G.O.P. to oppose the Justice Department at every turn.

“The reality is this appointment is meant to distract from, and slow down, our investigations,” said Representative Jason Smith, Republican of Missouri and chairman of Ways and Means, one of three congressional committees looking into the Biden family’s finances.

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Senator Chuck Grassley, Republican of Iowa, who had once called for Mr. Weiss to be made special counsel, said he no longer stands by that belief. “Given the underhanded plea deal negotiated by the U.S. attorney from President Biden’s home state, it’s clear Mr. Weiss isn’t the right person for the job,” Mr. Grassley said.

But Democrat-aligned groups saw something else in the Republicans’ about-face: disingenuousness.

“House Republicans’ opposition to Trump appointee David Weiss’s appointment as special counsel is nothing more than another political stunt,” said Kyle Herrig, the director of the Congressional Integrity Project, an advocacy group that defends President Biden from congressional investigations. “After months of calling for this, their dismay makes clear that they will stop at nothing to weaponize Congress to interfere with an ongoing investigation and harm Joe Biden.”