By inviting Fox News Channel’s Tucker Carlson to dig into 40,000 hours of footage from the January 6 riot, Speaker McCarthy fulfills a pledge to be transparent, but if his goal is blunting Democratic attacks, he’s throwing away his best cards and playing a weak hand.

On January 6, a splinter faction of a larger protest abused their constitutional rights to peaceful assembly and to petition for grievances. President Biden might have responded by delivering the unity he promised in the very election the rioters sought to disrupt. He chose instead to reduce the riot to yet another wedge issue.

Mr. Biden has likened the event to the Civil War, despite a disparity in the death tolls of some 600,000, but in the aftermath of that conflict, it was Republicans who turned that dark hour into a political cudgel, branding Democrats as the party of slavery, secession, and sedition, a tactic known as “waving the bloody shirt.”

President Lincoln, by contrast, sought to bind up the nation’s wounds. In his final public address, he asked the band to play “Dixie,” an act that outraged a Democratic actor, John Wilkes Booth, who declared that Lincoln’s remarks meant citizenship for black Americans and assassinated him a few days later to prevent it.

After the war, Republicans welcomed loyal Democrats back into the union, whereas Democrats today have refused to accept any Republican condemnation of the rioters, calling them complicit in acts of desecration. The GOP chose to fight such emotional rhetoric with facts, which is like trying to beat a royal flush with a pair of deuces.

By giving Fox News and Mr. Carlson an exclusive, Mr. McCarthy guaranteed that rival news outlets would go right on following the Democratic narrative, predisposed anyway to disregard a rival’s story as they did with the New York Post’s Hunter Biden exposé. Mr. McCarthy had to know that Democrats would focus on personality not, say, the protestors held without trial or the fact that not one of them has been charged with insurrection.

When I worked at Fox News Channel during its 1996 launch, we built a wall of separation between news and opinion. I asked Mr. Carlson via text if there was any concern about blurring that line, even if no one could expect him to reject such a huge exclusive.

Mr. Carlson wouldn’t discuss the network’s internal discussions, or that by giving him the videos while dragging his feet on making the videos “more widely available,” Mr. McCarthy provided the rest of the press a built-in excuse to ignore his documentation.

As a result of Mr. McCarthy putting all his chips on Fox News, millions of Americans who are not watching Mr. Carlson’s show or catching bites on social media will turn a blind eye to its fuller and more accurate portrayal of January 6.

Outlets are already running defense. NBC reported that Mr. Carlson’s report “falsely depicts Jan. 6 riot as a peaceful gathering.” CNN ran a headline stating, “Tucker Carlson, with Help From Kevin McCarthy, Tries to Sanitize the Very Real Violence of the January 6 Attack.” Senator McConnell agreed that Mr. Carlson “cherry-picked.”

Even the news department of Fox on cable, according to a Mediaite review, is “completely ignoring” Mr. Carlson’s work, although they are covering it online. Expect the videos to get shrugged off as “edited,” “snippets,” and “out of context,” and the story to be “old news” by the time Mr. McCarthy gives others the footage.

Since Mr. McCarthy chose to follow the partisan approach of the January 6 committee by focusing on conservative outlets, far from blunting Democratic attempts such as turning turn the so-called QAnon shaman, Jacob Chansley — who the footage shows being given a tour of the Senate — into the face of Republican opposition, they remain on the defensive with the electorate at large.

Mr. McCarthy’s choice to share the footage with Fox didn’t advance the goal of giving Americans a more complete understanding of January 6. Democrats are still waving the bloody shirt, and a nation that should be healing the wounds of the past generation remains as divided as at any time since the Civil War.