Donald Trump Jr
Prof Frank Bowman, says 17 Republican senators will need to back impeachment for it to succeed.
Donald Trump's two sons have rebuked Republicans for failing to back the president as he struggles to win re-election.
Trump's eldest son, Don Jr, accused the party of being "weak". His brother Eric warned: "Our voters will never forget you if your [sic] sheep!"
Senior Republicans such as Utah Senator Mitt Romney and Maryland Governor Larry Hogan have warned the Trump campaign against undermining the democratic process.
Don Jr took to Twitter to dish out his ire for those who may be eyeing up a presidential run in 2024.
"The total lack of action from virtually all of the '2024 GOP [Republican] hopefuls' is pretty amazing," he wrote.
"They have a perfect platform to show that they're willing & able to fight but they will cower to the media mob instead. Don't worry @realDonaldTrump will fight & they can watch as usual!"
The younger Trump later told supporters in Atlanta, Georgia - one of the key battleground states where votes are still being counted - that his father was right to mount legal challenges to the vote-counting process.
"I think the number one thing that Donald Trump can do in this election is fight each and every one of these battles to the death," he said.
By Alex De Waal
What led to Dr Sean Conley being forced to clarify the president's treatment?
Donald Trump Jr speaks at the 2020 Republican National Convention.
By Tara McKelvey
BBC White House reporter
By Jane Wakefield
By Cache McClay
BBC News, Washington
The US president said that wearing a mask was not for him, despite advice from health officials.
The BBC's Jeremy Bowen explains why the proposal has been lauded by the Israelis, but shunned by the Palestinians.
The businessman defended the president's character during his appearance on The View.