Donald Trump‘s legal team kicked off the bulk of its defence case by contending the president did not freeze a massive military aid package for Ukraine to investigations of top US democrats — and tried to undermine the legitimacy of impeachment itself.

The president’s lawyers started their second day of case-making by attacking the very nature of a presidential impeachment, with one of his lawyers telling senators it is “tantamount to domestic war”. Their case continued hours later with Pam Bondi, a former Florida state GOP attorney general, laying out the White House's version of what happened with former Vice President Joe Biden, his son Hunter Biden, and a Ukrainian energy company called Burisma. Bondi claimed the then-VP and son acted inappropriately as the father was leading the Obama administration's anti-corruption push there while his son sat on the company's board, which the UK government was investigating for money laundering.

Ms Bondi pushed a disputed narrative about the former vice president's involvement in the removal of a Ukrainian prosecutor who was investigating the company. She hinted VP Biden did so to help his son, but the Obama administration stipulated its own aid package for Ukraine on the ouster of that prosecutor because he was deemed by the West to be corrupt. "That is enough," she said.

Ms Bondi also criticised the House Democratic managers for not giving senators "the full picture," even though the one she laid out has been challenged by Democratic lawmakers and fact-checkers.

Neither Biden has been charged in either country with wrongdoing, something Ms Bondi excluded from her presentation.

Eric Herschmann, another Trump lawyer, followed and asked while noting Hunter Biden had no energy-specific experience: "Why would Burisma want Hunter Biden on its board? ... He had one qualification: He was Joe Biden's son."

But it was an attack on impeachment itself the team opted to lead with on Monday.

“It’s filled with acrimony and it divides the country like nothing else,” Mr Starr said in the Senate chamber of impeachment. “Those of us who lived through the Clinton impeachment understand that in a deep and personal way.”

Notably, Mr Starr did not contend Mr Trump is innocent of the actions House Democrats accused him of. Rather, he said impeaching a sitting commander in chief brings “grave disruption to the government ... regardless of what the president has done.”

Mr Starr began his presentation with a detailed lecture on impeachment, describing it as a flawed and outdated process. Saying other countries have all but abolished it, he declared it “fails to meet modern procedural standards of fairness”.

All the president's lawyers: The team fighting Trump's impeachment Show all 6 1 /6 All the president's lawyers: The team fighting Trump's impeachment All the president's lawyers: The team fighting Trump's impeachment Alan Dershowitz Dershowitz is a controversial American lawyer best known for the high-profile clients he has successfully defended. Those clients have included OJ Simpson, Jeffrey Epstein and Harvey Weinstein. One longtime Harvard Law associated told the New Yorker Dershowitz "revels in taking positions that ultimately are not just controversial but pretty close to indefensible." Getty All the president's lawyers: The team fighting Trump's impeachment Ken Starr Starr became a household name in the 1990s as the independent counsel who led the investigation that led to Bill Clinton's impeachment. That investigation began as a look into a real estate scandal known as Whitewater, and eventually led to impeachment after Mr Clinton lied under oath about having an affair with White House intern Monica Lewinsky. AP All the president's lawyers: The team fighting Trump's impeachment Jay Sekulow Sekulow is the president's longtime personal attorney, and, now, personal lawyer in the White House. He has been accused by former Rudy Giuliani associate Lev Parnas of being "in the loop" during the Ukraine scandal. Getty All the president's lawyers: The team fighting Trump's impeachment Pam Bondi Bondi is the former attorney general in Florida, and a longtime backer of the president's. She made a name for herself in Florida for taking hyper partisan stances on issues, and her penchant for publicity. She is likely to be a prominent public-facing figure during the trial. AFP/Getty All the president's lawyers: The team fighting Trump's impeachment Pat Cipollone Cipollone is the White House counsel, and leading the president's defence team. Getty All the president's lawyers: The team fighting Trump's impeachment Rudy Giuliani While not officially named as one of the president's impeachment lawyers, it is hard to ignore Giuliani's outsized role in this process. The former mayor of New York has been making headlines for months as he defends his client, and for his apparent role in the effort to compel Ukraine to launch the investigation into Joe Biden. We'll see how he figures in the actual trial, which he has said he would like to be a part of. Reuters

Attempting to discredit impeachment itself was a theme of the session’s opening hour.

Jay Sekulow, one of Mr Trump’s personal lawyers, led off for the defence, telling senators House Democrats had wrongly rebuked the president for actions that fail to clear the Constitution’s impeachment bar.

“If this becomes the new standard, the future is going to look a lot different,” Mr Sekulow warned senators.

The president’s defence team began its second day of laying out their case after the trial was rocked — and potentially changed — by a New York Times report that a former senior adviser to Mr Trump heard him say he intended to keep a military aid package for Ukraine frozen until that country announced probes of top US Democrats.

That contradicts the president’s claims that he held up aid over concerns about widespread corruption in the Eastern European country. Mr Trump on Monday morning denied Mr Bolton’s allegation.

Mr Sekulow did not mention Mr Bolton, but said Mr Trump never conditioned the military aid package on the Ukraine investigations he desired.

“Those are the facts,” he told senators, moments before the defence team played a video of Trump administration officials testifying before the House — in which they said there were no investigations announced after the aid monies were allowed to flow.

Michael Purpura, deputy White House counsel, soon walked the senators through a series of events, including more House testimony clips from administration officials he said shows Mr Trump was concerned about “burden-sharing” on Ukraine aid with America’s European allies and corruption inside Ukraine.

“It’s the same two convincing themes every time,” Mr Purpura said.

Mr Trump’s legal team is not expected to bring up the former White House official on Monday or Tuesday as they make and close their case. But the Ukraine aid and other allegations in the leak of his coming book now hangs over the entire proceeding, with two GOP senators — Susan Collins of Maine and Mitt Romney of Utah — signalling they likely will now join Democrats in voting to call Bolton as a witness. Two more Republicans would have to do the same, then the White House could claim executive privilege over Mr Bolton’s testimony, setting up a legal battle.

Sen. Mike Braun of Indiana told reporters he has talked with several Republican senators who have “grappled” with whether to support calling new witnesses, and believes Mr Bolton’s account of the military aid will change the “dynamic” around the trial.

Ken Starr: 'Like war, impeachment is hell'

Seeking to plant seeds of doubts about House Democrats’ intentions, the defence team played a video of House Speaker Nancy Pelosi handing her seven impeachment managers the pens she used to sign the articles against Mr Trump.

During that ceremony, Pelosi and other Democrats at times smiled. Some insisted on posing for pictures, with wide grins, alongside the speaker.