The Republican presidential candidate Nikki Haley’s demand for mental competency tests for politicians older than 75 is “absurd” and ageist, the Vermont senator Bernie Sanders said.

“We are fighting racism, we’re fighting sexism, we’re fighting homophobia, I think we should also be fighting ageism,” Sanders, 81, told CBS’s Face the Nation.

Sanders has mounted two strong challenges for the Democratic presidential nomination, the first in 2016 when he was 74.

Haley, 51, launched her 2024 campaign this week, calling for a “new generation” of leaders but offering few policy specifics except a call for political term limits and mental competency tests.

She has aimed that talking point at Joe Biden, the 80-year-old president, but not at Donald Trump, the 76-year-old former president who remains her only declared rival for the Republican nomination.

Asked on Fox News Sunday why she was a better choice for the nomination than Trump or anyone yet to declare, the former South Carolina governor said: “Why not me?”

“You know, I am a wife of a combat veteran. I’m a mother of two children.”

Haley said those children were struggling with the cost of buying a home and with the challenge of “woke education”, while her Indian immigrant parents were “upset by what’s happening at the border”.

Claiming she had “never worked in DC”, the former ambassador to the United Nations who was part of Trump’s White House cabinet and met with the president in the Oval Office, said it was “time that we start putting a fire on what’s happening in Congress”.

Repeating her call for term limits and “mental competency tests for people over the age of 75”, she said: “And what I do strongly believe is the American people need options. I don’t think you have to be 80 years old to be in Washington DC.”

Sanders told CBS: “I think that’s absurd. We are fighting racism, we’re fighting sexism, we’re fighting homophobia, I think we should also be fighting ageism.

“Trust people, look at people and say, ‘You know, this person is competent, this person is not competent.’ There are a lot of 40-year-olds out there who ain’t particularly competent. Older people, you know, you look at the individual, I don’t think you make a blanket statement.”

Sanders also discussed age, and its relevance for serving politicians, in an interview with the Guardian published on Sunday.

Speaking to promote his new book, It’s OK to be Angry About Capitalism, he said he expected Biden to run for re-election in 2024, when the president will be 82, and vowed to support that effort.

“Age is always a factor,” Sanders said. “But there are a thousand factors. Some people who are 80 or more have more energy than people who are 30.

“… There are a lot of elderly people with a whole lot of experience who are very capable of doing great work.”