For the past few months, a single senator — Tommy Tuberville — has blocked hundreds of promotions in the U.S. military.Karoun Demirjian, a congressional correspondent for The Times, explains what’s behind the senator’s blockade, and why military leaders say it’s becoming a threat to national security.Guest: Karoun Demirjian, a congressional correspondent for The New York Times.Background reading: 

• Tuberville’s bid to reverse a Pentagon policy ensuring abortion access for service members has delayed the smooth transfer of power at the highest echelons of the armed forces.
• Here’s David Firestone of Times Opinion on Tuberville’s blockade.

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