He stood there for more than thirty seconds—unable, apparently, to speak. Mitch McConnell, who has led Republicans with a kind of sinister shrewdness since 2007, had just frozen up while speaking publicly for the second time in a matter of weeks. “We’re gonna need a minute,” a concerned aide told reporters in Kentucky, where he had just spoken at a Northern Kentucky Chamber of Commerce event in Covington.

The question that preceded the lengthy pause—“What are your thoughts on running for reelection?”—has since given way to a new, more pressing one: Can the 81-year-old minority leader carry out the rest of his term?

It had already come up in July, when he stopped speaking mid-sentence during a routine press conference at the Capitol and had to be escorted away from the microphone. It was the most public health issue he had suffered in recent months. He insisted at the time that he was fine—maybe a bit dehydrated—and the incident was quickly eclipsed in the news cycle by Donald Trump’s two most recent indictments. But now, after a second such incident in about a month’s time, questions about McConnell’s health are getting a lot harder to ignore.

Publicly, Republicans have deferred to the Senate minority leader, who has sought to allay concerns about his ability to do the job. “I expect he’ll continue to be the Republican leader through this term,” Senator Rick Scott, who mounted an unsuccessful challenge to McConnell’s leadership last fall, told CBS News on Wednesday. But behind the scenes, there appears to be growing concern—and some frustration, perhaps, at how cagey McConnell and his team have been. “If we’re going to stick with him,” a GOP aide told Politico, “he kinda owes it to us to tell us what’s going on.”

Apart from his two freeze-ups, McConnell has fallen at least three times since March, when he suffered a concussion that sidelined him for weeks: “That fall affected him,” Senator Ron Johnson told my colleague Pablo Manríquez earlier this month. But at least two falls went undisclosed by his office, and McConnell himself has been tight-lipped about his health status: “I’m fine,” he told reporters at the Capitol in July, after returning to the press conference following his first public freeze-up.

After this most recent incident Wednesday, his team said that he had merely felt “lightheaded,” but that he would visit a doctor. Attendees at a fundraiser later Wednesday for Congressman Jim Banks—which McConnell attended, despite his concerning episode earlier in the day—told CNN that he seemed to behave normally: “Tough as nails,” one fellow attendee said. And several top allies told the outlet, through spokespeople, that he sounded fine when he called to offer them assurances about his condition. “The leader sounded like his usual self and was in good spirits,” Ryan Wrasse—a spokesman for Senate Republican Whip John Thune, who is widely regarded as a potential successor to McConnell—told CNN. (John Cornyn and John Barrasso, other McConnell allies who may be in line to take over as leader, also continue to stand behind him.)

But those reassurances may not do much to stop the growing succession chatter when the Senate returns from recess next week, following the long Labor Day weekend. They are also unlikely to tamp down concerns about the age of America’s leaders. That uncomfortable conversation, in the Senate, has mostly focused on 90-year-old Democrat Dianne Feinstein, whose health appears particularly diminished since returning to Washington after a prolonged bout with shingles earlier this year. Now, after his second freeze-up—during which he appeared noticeably thinner—that conversation will surely include McConnell, as well.