There was a fiery exhange of ideas during the third Democratic primary debate in Houston on Thursday night, as frontrunner Joe Biden came under attack from all sides.
The former vice-president, who is leading in the polls, was forced to defend his record as a centrist candidate best positioned to take on Donald Trump in the presidential election next year.
Ten candidates took part, a much smaller field than the 20 who qualified for the two previous debates in Miami and Detroit. And once again most candidates positioned themselves against Biden, who is competing for the Democratic nomination for the third time.
While much attention ahead of the debate had focused on Elizabeth Warren, who has built a strong profile throughout the summer, she had relatively few direct exchanges with Biden. Instead, it was former Obama cabinet member Julian Castro who tackled the former vice-president, leading to one of the stand-out moments of the night.
After challenging 76-year-old Biden on his comments on healthcare, the former housing and urban development secretary in the Obama administration said to Biden: “Are you forgetting what you said two minutes ago?” The intervention was widely seen as a comment on Biden’s age – and unfounded, given that the vice-president had not contradicted himself.
He also challenged the former vice-president's characterisation of himself as a representative of the Obama administration, saying: "I'm fulfilling the legacy of Barack Obama and you're not."
Minnesota senator Amy Klobuchar said that Castro's comments were "not cool", though New Jersey senator Cory Booker in a later interview implied that Castro was within his rights, noting that he had raised "legitimate concerns" about whether Biden is someone who can "get the ball over the line".
Nonetheless, while Biden performed slightly better than in the previous two debates, he had some moments that raised questions about his ability to successfully challenge Trump. In one answer to a question on segregation, he veered into comments on children and schooling, suggesting that parents should have “the record player on at night”, a reference that suggested he was out of touch with modern technology.
Several of the lower-polling candidates managed to make their mark. Former Texas congressman Beto O'Rourke, who has failed to build on the momentum of his Senate campaign last year, got one of the biggest cheers of the night when he tackled the issue of gun crime, which hit his home town of El Paso in July.
“Hell, yes, we’re going to take your AR-15, your AK-47,” he said, referring to the assault-type rifles that have been used in America’s most deadly shootings.
Indiana mayor Pete Buttigieg also performed well, his appeal to party unity striking a moderate and constructive note.
While California senator Kamala Harris had some good moments, some of her interventions fell flat, particularly an attempt to use Obama's "yes we can" motif to criticise Biden.
Overall, the three-hour debate saw candidates differentiate themselves on policy, particularly in relation to healthcare – a key issue heading into next year's election.
Biden challenged Warren and Sanders over their plan to adopt Medicare for All and abolish private healthcare, questioning how they would fund the proposal. But Warren defended the policy, arguing that ordinary families would pay less under her plan, while only wealthy individuals and businesses would see costs rise.
Meanwhile Biden came under pressure from Sanders for his decision to back the Iraq War.
The debate is unlikely to change the dynamics of the race, with frontrunners Biden, Warren and Sanders all holding their own during the three hours. What still remains unresolved is the ideological divisions within the party between those advocating a centrist approach and those embracing a more left-wing agenda.
The question of which strategy offers the best opportunity to defeat Donald Trump next year is likely to define the Democratic primary race in the months to come.