Having successfully blocked creation of an independent, bipartisan commission to investigate the Jan. 6 attack on the Capitol by supporters of then-President Donald Trump, Republicans are now intent sabotaging any kind of serious investigation. That became clear with House Minority Leader Kevin McCarthy’s (R-Calif.) selection of members to serve on the select committee formed to investigate the insurrection. House Speaker Nancy Pelosi (D-Calif.) must not allow his cynical gambit to spoil this opportunity to get to the bottom of the terrible events of Jan. 6.

Mr. McCarthy on Monday announced his five picks — Jim Jordan of Ohio, Jim Banks of Indiana, Rodney Davis of Illinois, Kelly Armstrong of North Dakota and Troy E. Nehls of Texas — for the 13-member committee. No sooner were the names revealed than Mr. Banks, who would serve as ranking minority member, issued a blistering statement that blasted Democrats, attacked the purpose of the committee and suggested Republicans might use it to attack President Biden. “I will not allow,” he said, “this committee to be turned into a forum for condemning millions of Americans because of their political beliefs.”

On Jan. 6, Mr. Trump’s supporters stormed the Capitol in an attempt to stop Congress from certifying the 2020 presidential election results. This was not a peaceful expression of political beliefs; it was a violent and criminal attempt to interfere with the democratic process. A federal judge underscored that fact on Monday when he sentenced a Jan. 6 defendant to eight months in prison, rejecting any notion that the events of that day were simple protest. “There were people storming through the halls of the Capitol saying, ‘Where’s Nancy?’ People were threatening the lives of members of Congress. That is more than a simple riot,” said U.S. District Court Judge Randolph D. Moss.

Because of how the committee was created, Ms. Pelosi will have final say on its membership. Her appointments — including Republican Rep. Liz Cheney (Wyo.) and Democratic Rep. Bennie G. Thompson (Miss.), the chairman of the Homeland Security Committee who will lead the panel — reflected a real seriousness of purpose. In contrast, Mr. McCarthy’s choices seem solely designed to make a circus of the proceedings. Ringleader, of course, would be Mr. Jordan, a persistent if not terribly skillful disrupter and provocateur. Mr. Jordan, Mr. Banks and Mr. Nehls all voted against certifying the results of the election despite the absence of voter fraud or major irregularities. Their complicity in feeding Mr. Trump’s lie about a stolen election is not compatible with any dispassionate investigation of the day’s events.

The committee has important questions to explore, including the role that Mr. Trump and the Pentagon played on Jan. 6; possible failures of intelligence; and, most of all, how to lessen the likelihood of a recurrence. Ms. Pelosi should approve the appointment only of legislators who are committed to answering those questions and uncovering the truth.