First, with no public fanfare, Republicans undertook two big voter-registration drives. One, which I helped run, used big data, technology and volunteers from the Texas Federation of Republican Women, College Republicans and county GOP organizations. Mr. Cornyn lent a wily former state GOP chairman, Steve Munisteri, to travel Texas stirring up volunteers and enthusiasm while the program’s director, Mitch Carney, led an effort that added 212,972 new Republicans to the voter rolls—at a cost of $7.90 each. The other effort, by the super PAC Engage Texas, used traditional methods, hiring nearly 200 workers to stand outside Department of Motor Vehicles offices and knock on doors. Before it was shut down by Covid-19, it registered another 105,697 Republicans at a cost of $70.10 each.

The combined total of 318,669 new Republicans would constitute almost half of Mr. Trump’s statewide margin of victory and one-third of Mr. Cornyn’s. But both efforts focused on key congressional and state House districts. In one congressional seat and at least four state House races, the numbers of new in-district Republican registrations were more than the winning GOP candidate’s margin.

Second, Texas Republicans mounted a big get-out-the-vote operation. Mr. Cornyn benefited from such efforts when he was elected a state Supreme Court justice in 1990 and state attorney general in 1998. Last year he directed his campaign manager, John Jackson, and Mr. Munisteri to re-create such an effort for this fall. They picked a young operative, Spencer Davis, to run it.