President Donald Trump and Republican allies are arguing that Sen. Kamala Harris would really be in charge if Democrats win the White House.

During the past week, Trump told Sean Hannity of Fox News that Harris would assume the presidency within “three months” of Biden’s inauguration. During a conversation with Rush Limbaugh, he warned that House Speaker Nancy Pelosi would “replace” Biden with Harris. And the president called her a “monster” during an interview with Maria Bartiromo of Fox Business.

At his first campaign rally since being hospitalized for the virus, Trump told a Florida crowd on Monday that Biden has “a lot of bad days coming.”

Former House Speaker Newt Gingrich said: “If voters understand the totality of her radicalism, they would conclude that she would be a very high-risk person to put in the White House.”

He went on to call Biden “docile” and Harris “aggressive.”

There are some signs that Trump’s message is resonating with his base.

“I’m scared that if Harris gets in, it will be a Harris administration ’cause old Joe’s got some issues,” said Bob Stanley, a retired orthopedic physician assistant who lives in Johnstown, Pennsylvania, and said he will be voting again for Trump.

For a running mate, the willingness of a vice presidential candidate to step in as commander in chief has long been a prime prerequisite. Either Biden, 77, or Trump, 74, will become the oldest president ever inaugurated.

Biden last released medical records in December 2019, during the Democratic primary. Biden’s doctor called him “healthy, vigorous” and fit to execute the duties of the presidency. He takes a statin medication for cholesterol and has a “persistent” atrial fibrillation, a type of irregular heart beat. He takes a blood thinner to prevent risks like blood clots or stroke.

A Pew Research Center poll released in August found that among Biden supporters, 31% called his age or health a concern in an open-ended question. Just 1% of Trump’s supporters said the same about the president, though the survey was taken before Trump contracted the coronavirus.

Harris and Vice President Mike Pence deflected in last week’s debate when asked if they had conversations with Biden and Trump, respectively, about procedures in the event of presidential disability.

Harris did not address the question directly or speak to Biden’s health at all, instead pivoting to their shared values and her own political background, an implicit nod to her fitness for the top job if need be.

“I serve on the Senate Intelligence Committee, where I’ve been in regular receipt of classified information about threats to our nation and hot spots around the world. I’ve traveled the world. I’ve met with our soldiers,” she said.