(CNN) Joe Biden was as good at Thursday night's debate as he's been in the entire campaign and perhaps close to as good as he could be.

In some scenarios of how the 2020 election breaks, such a solid but unspectacular showing could be enough for the former vice president to win the Democratic nomination and maybe even the White House.

After a summer marked by occasional gaffes suggested he might be a decade past his best, Biden personified one of his most winning characteristics -- resilience -- in steadying his front-running campaign. His performance in Houston is likely to quell fears that his third presidential bid could stall at any minute like his previous campaigns and leave questions about his deepest liabilities for another day. It keeps his core claim intact that he is the most electable Democrat in a fierce race with President Donald Trump

It helped that one of his rivals, former Housing and Urban Development Secretary Julián Castro defused the age question with a crude suggestion that Biden had memory problems that even appeared to make other candidates on stage blanch.

And since the night lacked a standout showing by Sen. Elizabeth Warren , who has been rising in the polls and media buzz, or anyone else on stage, the debate may therefore freeze the race in place with Biden as a clear but not prohibitive front-runner.

After appearing off his game in previous debates, Biden was sharper, traded jabs more easily with other candidates, and was stronger on policy -- his own and the weaknesses in the platforms of his foes for the nomination -- than ever before.

He made his strongest tilt yet at animating a center left argument for Democrats -- one that puts him at odds with the noisiest and most progressive elements of his party.

And he began to tease out the ideological debate with Warren and Vermont Sen. Bernie Sanders that could define this race. His message was that big aspirations on issues like health care are great -- but ultimately mean nothing without a plan to get them enacted in what is likely to be an unresponsive Congress.

Biden shows his liabilities as well

But Biden was far from perfect.

In one almost impossible-to-follow interaction, he came across as rambling and out of touch when he was asked about his past attitudes to historic racial discrimination.

He appeared to suggest that some African-Americans are poor parents, made a reference to technology that has been obsolete for years and then made an odd diversion to speak about Venezuela.

"We bring social workers into homes and parents to help them deal with how to raise their children," Biden said.

"It's not want they don't want to help. They don't -- they don't know quite what to do. Play the radio, make sure the television -- excuse me, make sure you have the record player on at night, the -- the -- make sure that kids hear words."

Castro, who was up next up, quipped: "Thank you very much. Well ... that's quite a lot."

Biden was unable to make an overarching argument for why Trump should be blocked from a second White House term. That's odd since his entire campaign is premised on the idea that the President is an assault on basic American values.

It was left to California Sen. Kamala Harris to pick up that theme and Biden might regret giving her an opening.

While he was more nimble on his feet, Biden still sometimes began a sentence as if he often didn't know where it ended.

Occasionally, he inadvertently stressed his age -- one of his campaign's biggest challenges given the taxing nature of the presidency and the potency of the youth vote in his party. For instance he opened the debate talking about President John Kennedy's moonshot. JFK is a legend for Democrats -- but also a figure from the mists of time for young activists who unlike Biden did not come of age in the era of Camelot.

Biden's explanation of his original support for the Iraq war was meanwhile confusing and mixed in a meandering argument about Afghanistan. Foreign policy is supposed to be his strength.

And Biden's repeated invoking of the presidency of Barack Obama -- who has become a talismanic figure in his party -- is beginning to look more like a crutch than a strong political point.

Biden is no longer the wisecracking, vibrant politician that he was in the 2008 Democratic race, where he was a sparkling debater who fell at the first hurdle in Iowa. The years since have been grueling for him, politically and especially personally.

But he is still there, unbowed and decent, and that may be an asset in a bitter political era when such qualities seem quaint.

Candidates offer Democrats an ideological choice

JUST WATCHED Biden, Sanders and Warren clash over health care Replay More Videos ... MUST WATCH Biden, Sanders and Warren clash over health care 01:58

Much of the 2020 campaign is beyond Biden's control, so all he can do is put forward the best version of himself.

If Democrats decide that they want a progressive icon who inspires the liberal base and promises to ignite a social revolution that remakes the face of politics -- he has no chance.

In that case, Warren or even Sanders have an opening. If a charismatic candidate currently in the second tier like Harris or New Jersey Sen. Cory Booker suddenly catches fire, the former vice president could be left flat-footed.

But if Democrats reason that the country needs a return to a more traditional politics, a period of peace and presidential dignity after the daily eruptions from Trump's White House and a moderate -- then it might be his time.

Given that equation, Biden must prove he can both make the center left case crisply on stage and that he can parry attacks from rivals who are far less vicious than the President.

On balance, that was what Biden did on Thursday.

While accepting a need for big reform on issues like health care -- Biden was mindful of general election voters and moderate Democrats who balk at the radicalism of some of his rivals.

Clumsy attacks

And the former vice president was able to profit from some clumsy attacks from other candidates.

Castro, the former secretary of Housing and Urban Development in the Obama administration, made a poorly received jab at Biden's age, when he snapped : "Are you forgetting what you said two minutes ago?"

The attack -- a move by a candidate desperate for traction in the race -- is likely to go down poorly among Democrats for whom Biden is a much loved and respected figure. It also committed the sin of mirroring one of Trump's on the 76-year-old Democratic veteran.

Sanders stung Biden into a passionate rejoinder and gave him a political opening when he said his health plan was the only one that could ensure someone who got cancer would not go bankrupt.

"I know a lot about cancer, let me tell you something. It's personal to me," said Biden who lost his beloved adult son Beau to the disease in the latest of a string of family tragedies.

It helped Biden that Warren had a quiet night -- so his main foil in the progressive vs. moderate contest was Sanders, whose voice, apparently affected by a cold, sounded more abrasive than normal.

One of Biden's most touching qualities and one of his most powerful political skills is connecting with voters through the prism of his own life of grief and loss.

He invoked the death of his first wife and daughter in a car crash and Beau's passing in his final answer about how he would show residence as president.

"For me, the way I've dealt with it is finding purpose. And my purpose is to do what I've always tried to do and stay engaged in public policy.

"But there's a lot of people been through a lot worse than I have who get up every single morning, put their feet one foot in front of another, without the help I had," he said. "There are real heroes out there. Some real heroes."