Mike Pence’s former chief of staff Marc Short joined several senior Republicans in rallying to defend the former vice-president on Sunday in his escalating feud with Donald Trump over the legitimacy of the 2020 presidential election.

Some of Trump’s advisers on the 2020 election were like “snake oil salesmen”, Short said on Sunday.

Pence angered the former president this week by rejecting Trump’s false claim that he had the power to overturn Joe Biden’s victory by refusing to accept results from seven contested states.

At a conference hosted by the conservative Federalist Society in Florida on Friday, Pence delivered his strongest rebuke to date of Trump’s election lies, declaring that it was “un-American” to believe that any one person had the right to choose the president.

On Sunday, Short, and Republican senators John Barrasso, Lisa Murkowski and Marco Rubio, were among senior party figures who backed Pence’s position, adding their voices to a backlash by other prominent Republican figures apparently growing weary of Trump’s continued obsession with his election defeat and subversion of democracy.

“There’s nothing in the 12th amendment or the Electoral Count Act that would afford a vice-president that authority,” Short told NBC’s Meet the Press, describing advisers who told Trump that Pence could send election results back to the states as “snake oil salesmen”.

“The vice-president was crystal clear from day one that he didn’t have this authority.”

Pence, as president of the US senate, certified Biden’s victory in the early morning of 7 January 2021, hours after a mob incited by the defeated president launched a deadly insurrection on the US capitol.

Short, who sheltered with Pence in the Capitol as the mob outside erected a gallows and called for the then vice-president to be hanged, added that his boss had no alternative but to certify Biden’s win. “He was following what the Constitution afforded the vice-president … he was doing his duty, which was what he was required to, under an oath to the constitution to defend it,” he said.

“Unfortunately the president had many bad advisers, who were basically snake oil salesmen giving him really random and novel ideas as to what the vice-president could do. But our office researched that and recognized that was never an option.”

Short also attacked the Republican party’s position – crystalized this week in a widely derided censure motion for Liz Cheney and Adam Kinzinger, the only two Republicans on the House committee investigating the insurrection, that the January 6 rioters were engaging in “legitimate political discourse”.

“From my front-row seat, I did not see a lot of legitimate political discourse,” said Short, who along with the vice-president had to be hustled to a place of safety as the mob rampaged through the building.

“They evacuated us into a secure location at the bottom of the Capitol. There was an attempt to put the vice-president into a motorcade but he was clear to say: ‘That’s not a visual I want the world to see of us fleeing.’ We stayed there and worked to try and bring the business back together and complete the work that night.”

Barrasso, a Wyoming Republican and ranking member of the Senate foreign affairs committee, agreed with Short’s assessment in an appearance on Fox News Sunday.

“I voted to certify the election, Mike Pence did his constitutional duty that day,” Barrasso said.

“It’s not the Congress that elects a president, it’s the American people.”

Rubio, a Republican Florida senator, told CBS’s Face the Nation that he had long known that Pence lacked the authority to bend to Trump’s will. “I concluded [that] back in January of 2021, when the issue was raised,” he said. “I looked at it, had analyzed it, and came to the same conclusion that vice-presidents can’t simply decide not to certify an election.”

Rubio refused to say whether he thought the riot was political discourse, but added: “Anybody who committed crimes on January 6th should be prosecuted. If you entered the Capitol and you committed acts of violence and you were there to hurt people, you should be prosecuted.”

Murkowski, an Alaska Republican, is among the supporters of an “aggressive” bipartisan effort in Congress, criticized by Trump, to overhaul the 1887 Electoral Count Act and enshrine in statute that a vice-president has no role in deciding a presidential election.

“We’ve identified clearly some things within the act, the ambiguities that need to be addressed,” she told CNN’s State of the Union.