During the latest debate, candidates on stage mentioned the Australian bushfire crisis as evidence that the US needs to treat climate change as a national emergency and slash carbon emissions. Democratic presidential candidates Elizabeth Warren and Bernie Sanders share a tense moment after the debate. Credit:Patrick Semansky While their tone remained civil throughout the debate, Sanders and Warren essentially accused each other of lying about what occurred at a private meeting in December 2018. After the debate, video footage showed Warren declining to shake Sanders' hand and the pair exchanging what seemed to be tense words. Warren says that Sanders told her he did not believe a female candidate could win in 2020, a claim he vehemently denies. Asked by a moderator why he made the remark, Sanders said: "Well, as a matter of fact I didn't say it. Anybody who knows me knows it's incomprehensible that I would think that a woman could not beat the President of the United States. Go to YouTube today: there's a video of me 30 years ago talking about how a woman could become president of the United States."

While noting that "Bernie is my friend" Warren repeated her belief that Sanders made the claim in their meeting. Democratic presidential candidate Pete Buttigieg referenced the Australian bushfire crisis during the debate. Credit:AP "Look, this question about whether or not a woman can be president has been raised, and it's time for us to attack it head-on," Warren said, asking the audience to compare the electoral records of the men and women on the stage. "Collectively, they have lost ten elections," Warren said, referring to the male candidates. "The only people on this stage who have won every single election that they've been in are the women. [Minnesota Senator Amy Klobuchar] and me," Warren said. "And the only person on this stage who has beaten an incumbent Republican anytime in the past 30 years is me." Speaking about the threat posed by global warming, Buttigieg said: "In Australia, there are literally tornadoes made of fire taking place. This is no longer theoretical, this is not off in the future. We have to ensure it doesn't get any worse."

Billionaire candidate Tom Steyer also referenced the "gigantic climate issue in Australia". Early in the debate, Biden and Sanders clashed over Biden's support for the 2003 Iraq War – a decision Sanders said shows the former vice president lacks foreign policy judgment. Analysis: How the frontrunners fared in seven rounds of debates Democratic presidential candidate and former Vice-President Joe Biden. Credit:AP Joe Biden: The former Vice-President can be grateful that elections aren't decided by debate performances alone. Particularly in the early rounds, the 77-year old's answers were rambling and lacked sharpness. But Biden steadied himself in later debates, showing flashes of the experienced, mainstream, charismatic candidate many Democrats long for.