"The real issue is his lack of the kind of temperament to be commander in chief and to be president," Sen. Tim Kaine said of Donald Trump. | Getty Kaine questions Trump attacking Clinton 'stamina'

When it comes to Donald Trump's repeated assertion that Hillary Clinton "lacks the mental and physical stamina" to be commander in chief, the Democratic nominee's running mate, Tim Kaine, cannot figure out what that means.

"I have no idea what he's talking about," the Virginia senator said in an interview with NBC's "Today" taped Tuesday and aired Wednesday.


Kaine drew attention to "the incredible amount of work" that Clinton did as secretary of state, including her travel schedule. "And then look at the grueling nature of this campaign," added Kaine, speaking to NBC News' Savannah Guthrie alongside his wife, Anne Holton, the former secretary of education for Virginia.

"What do you think is really going on, if he questions her physical stamina?" Guthrie asked, to which Kaine responded, "He's trying to deflect attention. The real issue is his lack of the kind of temperament to be commander in chief and to be president. And voters see that. They sense that."

Trump repeated the same concerns about Clinton's "stamina" later Tuesday evening in Wisconsin amid ongoing speculation about the former secretary of state's health. The Clinton campaign hit back at the "deranged conspiracy theories" on Tuesday, resharing the candidate's 2015 medical assessment from her internist.