Mr. Talarico, the Democratic nominee for Senate in Texas, showed up at a music festival, saying he had been at home with “a nasty case of the flu.”

As enrollment for Medicare Advantage begins this month, older Americans are confronting fewer options because insurers are discontinuing coverage in many areas.

Legal experts say the former Army officer convicted in a 2009 mass shooting could face a narrow, rushed path to appeal a public execution by firing squad.