Jimmy McCain, a son of former Arizona senator and 2008 Republican presidential nominee John McCain, said this week he has registered as a Democrat and will vote for Vice President Kamala Harris, a valuable nod of support for the Democratic nominee in a battleground state.

Jimmy McCain said he had been an independent since leaving the Republican Party after Donald Trump became its standard bearer in 2016. He decided during a nine-month overseas deployment that just ended to switch his registration to Democratic and announce it publicly. His decision was first reported by CNN.

He said he was further “fired up” by the decision after seeing Mr Trump’s campaign visit to Arlington National Cemetery, a visit that Ms Harris called a “political stunt” that “disrespected sacred ground”.

Mr Trump has had a fraught relationship with the McCain family since he denigrated the senator’s status as a war hero during his 2016 campaign.

Jimmy McCain said it was personally difficult for him to hear his father disrespected, but he said his father chose a public life and Americans are allowed to criticise their leaders.

“With Arlington, the people who are buried there gave their lives and the ultimate sacrifice,” Mr McCain said. “They don’t get a political opinion. We don’t know what those people felt, thought, what they believed. We know they believed in their country and that’s about it.”

Mr Trump said he was invited to Arlington by the families of marines killed in a suicide bombing during the chaotic US withdrawal from Afghanistan. His campaign released statements from the relatives accusing Ms Harris of playing politics with the issue.

Jimmy McCain, 36, enlisted in the US Marines as a teenager and served for four years. He reenlisted in the Army National Guard and was later commissioned as an officer, currently holding the rank of 1st lieutenant.

Ideologically, Mr McCain said he is a moderate.

“I’m a centre man who cares about his country more than anything,” Mr McCain said.

Cindy McCain, the late senator’s widow, endorsed President Joe Biden shortly before the 2020 election, a vote of confidence that helped the Democrat eke out a narrow win in Arizona with support from Republicans disaffected with Mr Trump.

Mr Biden appointed Mrs McCain to be the US ambassador to the United Nations food and agriculture agencies in Rome, where she is now executive director of the UN World Food Programme.

A navy pilot, John McCain was shot down over North Vietnam in 1967. He was captured, beaten and held prisoner for more than five years, refusing to be released ahead of other American servicemembers.

Mr Trump said of John McCain: “He’s not a war hero. He was a war hero because he was captured. I like people who weren’t captured.” Mr McCain later angered Mr Trump with his dramatic thumbs-down vote against repealing Barack Obama’s health care law.

Mr McCain represented Arizona in Congress for 31 years until his death in 2018 from an aggressive brain tumour and built a national reputation as a “maverick” willing to buck his party. While he sometimes took criticism from the Republican base and faced fierce primary challengers, he was overwhelmingly re-elected and remains a beloved figure in the state.