For the first charge, investigators allege Trump used his office to withhold almost $400m in military aid in exchange for Ukraine's commitment to investigate Former Vice President Joe Biden's son Hunter's involvement with Ukrainian gas company Burisma. More to the point, Trump, his legal team and congressional Republicans, led by Senate Majority Leader Mitch McConnell, are entirely focused on giving Republican base voters some talking point they can cling to in order to justify supporting a president who did all these awful things.
"Ambassador Bolton essentially confirms the president committed the offences charged in the first article of impeachment", he said at a press conference, referring to the House of Representatives' abuse of power impeachment article.
Bolton sent the White House a copy of his upcoming book on December 30. If Republican leaders succeed in blocking new evidence, the Senate would move quickly to a final vote where senators would vote "guilty" or "not guilty" on the two charges against Trump - abuse of power and obstruction of Congress.
The impeachment trial rules provide for a two-step process on whether to subpoena witness and documents, with an initial vote on whether to consider doing so and, if approved, subsequent votes to actually call witnesses or demand documents.
"It's filled with acrimony and it divides the country like nothing else", Starr said of impeachment.
Elizabeth Warren, a presidential campaigner like Biden but also a Senate juror, told reporters she found Dershowitz's arguments "nonsensical".
Bolton's book directly ties the release of USA military aid amounting to $390 million to Ukraine investigating Biden and his son, Hunter, to help Trump's reelection campaign.
Some moderate Republicans, including Senators Mitt Romney and Susan Collins, said the disclosures were likely to sway at least four Republicans to call Bolton to testify, which would give Democrats the votes necessary in the Republican-led Senate to summon him.
Impeachment trial of President Trump
Trump's defence team, however, side-stepped the Bolton issue as they defended their client in the Senate on Monday. Biden campaign spokesman Andrew Bates dismissed Ms Bondi's allegations, saying they had been widely discredited.
Starr, whose independent counsel investigation into President Bill Clinton resulted in his impeachment - he was acquitted by the Senate - bemoaned what he said was an "age of impeachment".
The president's defense team spent Monday accusing Democrats of improperly using impeachment as a weapon to get rid of a president they simply don't like.
Trump's false claim that the House "never even asked" Bolton to testify came on the heels of a major New York Times report about the former national security adviser's forthcoming book.
In 1998, Alan Dershowitz had correctly argued that committing an actual crime wasn't required to impeach a president, according to the U.S. Constitution and the founding fathers who wrote it. Senator Susan Collins of ME said the news reports about Bolton "strengthen the case for witnesses and have prompted a number of conversations among my colleagues".
Bolton was sacked by Trump in September after 17 months in the job.
Senate Majority Leader Mitch McConnell didn't know about Bolton's book, his office said. Many Republicans took the position that the Bolton news shouldn't affect how the defense lawyers lay out their case. On Monday Sen. Angus King, I-Maine, told NPR he expects there will be between five and 10 Republicans who will decide to vote in favor of receiving additional testimony - more than enough needed to force the issue.
Mr Bolton has said publicly he would testify if he gets a legal summons, however, ignoring the wishes of the White House lawyers who want him to lay low. "The Room Where It Happened; A White House Memoir" is to be released March 17.
Over the course of the afternoon, Bondi, the former Florida attorney general, and Herschmann featured clips of the elder Biden talking about his work in Ukraine, as well as footage of his son's recent televised interview about Burisma. "What is there to defend?"