Joe Biden did what he needed to -- avoid major blunders -- in the latest debate featuring the top Democrats in the 2020 race for the White House, but the frontrunner faced lingering doubts Friday about his ability to take on President Donald Trump.
The centrist former vice president weathered sustained criticism from his rivals on Thursday, far-left Senator Bernie Sanders in particular, on issues from health care and immigration to foreign policy.
In extended exchanges that highlighted the party's ideological schism over health care and the cost of shifting to a government-run universal coverage system, Biden was often in the limelight, occasionally going on the offensive against rivals.
The 10 candidates agreed on the need to defeat Trump, yet the president's record was not a mainstay of the event. There was no mention of a potential impeachment, something Democratic lawmakers are grappling with.
Next to Biden, progressive Senator Elizabeth Warren, who has risen to joint-second alongside Sanders in polling, breezed through largely unscathed, avoiding personal attacks and crisply outlining policy proposals.
Analysts saw Biden's first half hour, when he defended his health plans against Warren and Sanders and challenged them on the costs of their proposals, as among his most engaging debate performances.
But by the second half of the nearly three-hour marathon the frontrunner appeared less steady and Julian Castro, a former cabinet colleague under Barack Obama, launched an unwarranted attack on the 76-year-old over a memory lapse that hadn't happened.
- 'Biden's shakiness' -
Biden survived the jab, and it was a low point of the three debates for Castro, who was immediately upbraided by commentators pointing out that it was he, and not Biden, who had his facts wrong.
The exchange nevertheless brought into the open what many have wondered behind closed doors: whether Biden has the stamina and mental acuity to prosecute an exhausting campaign over the next 14 months.
"There's a lot of people who are concerned about Joe Biden's ability to carry the ball across the end line without fumbling," Senator Cory Booker, who departed from his normal position as courteous unifier, told CNN after the showdown.
"And I think that Castro has some really legitimate concerns about, can (Biden) be someone in a long, grueling campaign that can get the ball over the line?"
Biden has maintained a solid grip atop the polls throughout the campaign, despite a slippage in the past week as Warren has gained ground.
He is widely seen as the most electable against Trump -- but being the top contender brings more scrutiny.
Straightforward questions were answered with incoherent word salads and Twitter collectively raised its eyebrows as Biden referred to Sanders as "the president."
Memes were plastered across social media and heads scratched as he made an outdated reference to record players while answering a question about slavery.
Five months before the first nomination votes are cast in Iowa, the evening may not have moved the needle dramatically, but Biden's rocky moments at debates and campaign events may chip away at voters, University of Virginia politics expert Kyle Kondik said.
"I do wonder if Biden's shakiness, displayed persistently over time, may eventually erode the advantage he currently enjoys as the candidate perceived by most as the best option against Trump," Kondik told AFP.
"But if that is a problem, it may take months for it to do him damage we can see in polling."
- 'A house divided' -
Several lower-tier candidates fared well Thursday including ex-congressman Beto O'Rourke, whose passionate appeal for an end to gun violence after two mass shootings last month in his native Texas -- and his controversial call for mandatory buybacks of military-style assault weapons -- drew headlines.
Pete Buttigieg won plaudits for his frank and eloquent recollection of coming out as gay while mayor of South Bend, Indiana.
Senator Amy Klobuchar, positioned in the same moderate lane as Biden, had a solid performance, rising above the fray during heated personal bickering.
"A house divided cannot stand," she declared. "That is not how we're going to win this."
Warren, of Massachusetts, shared the stage with Biden for the first time, but maintained discipline and focused on her message of ending the "corruption" of a system she says rewards the wealthy and punishes the working class.
"Warren is behaving like a frontrunner, and she is unquestionably one of the leading candidates," Kondik said.
"As such, she has less incentive to mix it up with the others."