You might think that, in his quest to quell the coronavirus, President Joe Biden would be ready to try anything. But there are indeed some things he won’t try, and the reason is a familiar one. Biden’s vaccination drive has the feel of a political campaign that’s targeting the persuadable middle, when what’s really needed is a novel way to reach the proudly irrational. He’s using many of the same tools he employed in 2020: celebrity endorsements and door-to-door contacts, TV ads and the bully pulpit. Fewer and fewer unvaccinated Americans are heeding the message. Compared with an average of more than 3.3 million doses a day in April, only about half a million people are now getting vaccinated on a given day. Nearly one-third of the adult population hasn’t gotten a single dose of a COVID-19 vaccine at a time when the far more infectious Delta variant is sweeping the nation. There’s no assurance that more of the same will produce a better result... One option that administration officials have privately discussed is requiring the 2.1 million members of the federal workforce to get vaccinated, a senior official told me. (Private employers are already free to demand that their workers be vaccinated before returning to the office.) As commander in chief, Biden could also order all 1.3 million members of the active-duty military to get injections. “We get shots for everything,” H. R. McMaster, a retired Army general and former national security adviser under Trump, told me. “And the vaccine is far from experimental, like the botulinum vaccine was prior to Desert Storm” in 1991. (Military leaders have signaled that they might require COVID-19 shots for troops once the FDA gives full approval to the vaccines, which could happen this fall.)