The Fox News star Jeanine Pirro addressed the matter on “Hannity” on Thursday night. “You’ve got this guy Smirnov who was a respected confidential informant for 10 years by the F.B.I.,” she said. “They paid him money, he was so credible. Now, all of a sudden, a couple months ago, they decide, ‘Oh, he’s not credible,’ because he’s claiming that, you know, Joe Biden and Hunter Biden were engaged in a problem.”

Margot Cleveland, a correspondent at The Federalist, a right-leaning online outlet, argued that David C. Weiss, the special counsel who has been investigating Hunter Biden and who charged Mr. Smirnov last week, is the guilty party. Ms. Cleveland said the failure of Mr. Weiss to look into the informant’s background earlier had allowed him to continue “working to interfere in our election and pushing who knows what other lies to the F.B.I.”

“One thing is certain,” Ms. Cleveland wrote, “even if Smirnov is guilty, that does not exonerate Weiss.”

Others insisted that the case against the Bidens was still solid. The Daily Caller drew a comparison between Mr. Smirnov and Christopher Steele, the former British spy, whose allegations about collusion between Russia and Mr. Trump during the 2016 election were widely discussed in the news media. Why, the outlet pondered, was Mr. Steele not charged with lying to the government?

Attempts over several years by congressional Republicans to advance their claims that Mr. Biden and his son accepted bribes, or were involved in corrupt dealings, have been repeatedly shot down or produced no credible evidence. That did not stop a writer at The Gateway Pundit, a digital outlet that frequently traffics in conspiracies embraced by the right, from arguing that Mr. Smirnov’s credibility was in fact unblemished, and his allegations still sound.

“Alexander Smirnov NEVER ‘spread Russian disinformation,’” Cristina Laila, an associate editor, wrote. “No one is falling for this Russia Hoax 2.0 you’re peddling.”