Kamala Harris makes a decisive intervention, Joe Biden stumbles and the generation gap yawnsKamala Harris was the night’s big success story. Photograph: Joe Raedle/Getty ImagesIt was the second and last night of Democratic presidential debates in Miami, and sparks were flying. Here are the five big takeaways: 1\. Joe Biden takes incoming fireIt was the big question: how would the former vice-president and current comfortable frontrunner fare once he finally got in front of the cameras flanked by rivals, some decades his junior?Until Thursday night, Biden had kept public exposure to a minimum. But there was nowhere to hide under those brutal TV lights, and at the end of two hours Biden came off stage looking decidedly more worn than when he entered it.He began sure-footedly. His opening words were “Donald Trump” – a pointed reminder that Biden’s main claim to the nomination is his conviction that he is the candidate to unseat the US president. “Donald Trump thinks Wall Street built America. Ordinary working-people Americans built America,” he said.But then it started slipping. That carefully arranged mannequin of dependable Joe, the politician who gets the job done, the friend and deputy to Obama, started sliding.Biden came across as diffident, tentatively raising a finger when he wanted to speak – a manner that had even the NBC News hosts baffled. He spoke most passionately about what he had done in the past, rather than what he dreamed of doing in the future.Asked to state the one big reform he would push in his first term as president, he replied: “The first thing I would do is defeat Donald Trump.”An older guy who doesn’t get the question, let alone answer it. At worst, Biden started to look the one thing that he must avoid to retain his frontrunner status: like a man watching the world spin beyond his control. 2\. Kamala Harris seizes the dayIf Biden looked rattled, he had Kamala Harris to thank. From the start of the debate , she had the feel of a politician who had fire in her belly and wind in her sails.It’s been a while coming. Harris has struggled to articulate her vision, and has been criticized for her record as California’s former top prosecutor.But on Thursday she turned that around, transforming her law enforcement credentials from a vulnerability into a weapon. “America does not want to witness a food fight; it wants to know how to put food on the table,” she admonished the other nine candidates on stage like naughty children as they squabbled.Then came the one-liner that will probably go down in the annals alongside “Senator, you’re no Jack Kennedy”.Harris already had Biden against the ropes over his recent statements about the “civility” of having worked productively in the US Senate with notorious racial segregationists. They got things done together, Biden had argued, including in opposing federal bussing of children to desegregate schools.“I do not believe you are a racist,” Harris opened while addressing the former vice-president. You knew from the chill that crossed Biden’s face that history was in the making.“It’s personal, it was hurtful, to hear you talk about the reputations of two US senators who built their careers on segregation,” she continued. Biden stiffened.And then the killer lines: “There was a little girl in California who was part of the second class to integrate their public school and she was bussed to school every day. That little girl was me.”We’ll have to wait to learn whether the exchange was the beginning of the end for Joe Biden’s presidential hopes. But we already know that this is the beginning of the beginning for Kamala Harris. 3\. The great generational divideThere are exactly 40 years separating the youngest candidate on stage – Pete Buttigieg, 37, and Bernie Sanders, 77. And it showed.Much as they tried to project their experience and strength, Biden and Sanders found it difficult to hold the line. Eric Swalwell, a congressman from California, 38, broke the taboo subject by announcing it was time to “pass the torch”. “I’m still holding on to that torch”, Biden replied.Buttigieg alluded to the generational issue more subtly – as Buttigieg tends to do, asking viewers to “help me deliver that new generation to Washington before it’s too late”.Michael Bennet, Colorado senatorBennet raised his national profile earlier this year when the senator, typically known for his congeniality, delivered a fiery speech on the Senate floor, accusing Republican senator Ted Cruz of shedding 'crocodile tears' over the government shutdown.Joe Biden, former vice presidentBiden unsuccessfully ran for the nomination in 1988 and 2008, and his campaign is likely to be dogged by controversy after allegations from several women they were left feeling uncomfortable by their physical interactions with him. If successful, Biden would become the oldest person to be elected president in US history.Bill de Blasio, New York mayorNow in his second term as mayor of New York City, De Blasio is a hometown foe of Donald Trump's running on the message that there's plenty of money in the country but it's in the wrong hands. With a progressive track record but a chorus of critics in New York, can this Democrat overcome his late start and win the chance to take on Trump?Cory Booker, New Jersey senatorBooker first made a name as the hands-on mayor of Newark. Known for his focus on criminal justice reform and impassioned speeches on immigration, he has though been criticized for ties to Wall Street.Pete Buttigieg, South Bend mayorButtigieg wants to be the first openly gay millennial president. A Harvard graduate and Rhodes scholar, he became the youngest mayor of a mid-size US city at the age of 29. As a Navy Reserve lieutenant he deployed to Afghanistan.Julián Castro, former housing and urban development secretaryCastro casts himself as an antidote to Trump and the adminstration's hardline immigration policies. The grandson of a Mexican immigrant and raised by single mother, the 44-year-old Democrat is one of the most prominent Latinos in Democratic politics.John Delaney, former Maryland congressmanHe has delivered his message of pragmatism to voters in all 99 of Iowa’s counties since he officially kicked off the race in July 2017. The multimillionaire banking entrepreneur wants to build a big-tent party that appeals to independents and moderate Republicans.Tulsi Gabbard, Hawaii congresswomanAn Iraq war veteran who has vowed to run a campaign focused on issues of 'war and peace'. Gabbard made history as the first Samoan American and the first Hindu elected to Congress. But progressives are wary of her past conservative views on on social issues.Kirsten Gillibrand, New York senatorYears before the MeToo movement, the New York senator was leading efforts in Congress to combat sexual assault in the military and on college campuses. The former corporate lawyer has embraced a slate of economic ideas supported by the party’s progressive wing.Mike Gravel, former senator of AlaskaAt 88, Gravel will be the oldest candidate to be run for the nomination. However, according to his campaign, the staunch non-interventionist is not running to win, but to challenge Democratic orthodoxy on foreign policy. Will this little-known quixotic figure succeed?Kamala Harris, California senatorHarris is one of Trump’s fiercest critics, and has built a national reputation grilling administration officials during their confirmation hearings. A former state attorney general and the daughter of immigrants from India and Jamaica, Harris believes she has the unique profile to take on Trump.John Hickenlooper, former Governor of ColoradoBefore he served two terms as governor of Colorado, the 67-year-old Democrat worked as a geologist for a petroleum company. After a lay off, he switched careers and opened a successful brewpub in Denver that helped to revitalize the city’s downtown.Jay Inslee, Governor of WashingtonInslee is running as the “only candidate who will make defeating climate change our nation’s number one priority”. As the country experiences more powerful hurricanes, scorching wildfires and submerged coastlines, polls show public concern is growing.Amy Klobuchar, Minnesota senatorOn Election Night 2018, Klobuchar coasted to a third term as senator in a state Trump almost won. Next morning she was on every short list of potential presidential candidates. Supporters say her success with rural voters makes her a formidable candidate in the Rust Belt, while her calm demeanour provides a clear contrast with Trump.Wayne Messam, mayor of Miramar, FloridaFacing long odds, Messam, the son of Jamaican immigrants to the US and a former receiver for the Florida State Seminoles football team, is tossing his hat in the ring anyway. The 44-year-old businessman became Miramar’s first black mayor when he was elected in 2015. Seth Moulton, Massachusetts congressmanThe Harvard educated Marine veteran arrived in Congress with a bang, after unseating a nine-term Democratic incumbent in a Massachusetts primary in 2014. Moulton has continued to make waves by calling for 'generational change' in Democratic leadership and supported an effort to block Nancy Pelosi from becoming House Speaker in 2018.Beto O'Rourke, former Texas congressmanA one-time guitarist for an El Paso punk band called Foss, O’Rourke had kept a relatively low profile as a three-term congressman with little name recognition. He rose to national prominence during the 2018 midterms, when his bid to unseat Senator Ted Cruz garnered unprecedented grassroots support and a historic fundraising haul.Tim Ryan, Ohio congressmanElected to Congress in 2003 at just 29, Ryan represents the blue-collar voters Democrats hope to win back in 2020. He won national attention when he challenged Nancy Pelosi for Democratic leadership in 2016. He has continued to push for a generational change in leadership. Bernie Sanders, Vermont senatorSanders turned a long-shot, anti-establishment bid for the presidency into a “political revolution” that energized the party’s progressive base. His political career began nearly 40 years ago, but it wasn’t until his 2016 run that Sanders became a national figure as a new generation of Democrats – and 2020 contenders – embraced his populist economic policies.Eric Swalwell, California congressmanRaised in Iowa and California, the 38-year-old Democrat would be among the youngest candidates in the race. Swalwell serves on the House Permanent Select Committee on Intelligence investigating Russian collusion, a position that has earned him frequent appearances on cable news shows.Elizabeth Warren, Massachusetts senatorHer sharp criticism of Wall Street and big corporations has made Warren a favorite among progressive activists, and she will campaign on a message of a rigged economic system and income inequality.Marianne Williamson, authorThis is not the spiritual guru and a new age author’s first foray into politics: in 2014, she mounted an unsuccessful congressional bid in California. Her entry adds some star-power to the race that may attract more celebrities.Andrew Yang, businessmanA former tech executive and entrepreneur running the longest of long shot campaigns centered on the perils of automation. His central plank is a plan to give every American adult a salary of $1,000 per month, paid for by a tax on companies that benefit the most from automation.Lauren Gambino, Sam Morris and Martin Belam 4\. A good night for …Kamala Harris, obviously.Pete Buttigieg. The mayor of South Bend, Indiana was challenged over his handling of the recent fatal shooting in his town of a black man by a white policeman who had his body camera turned off. He weathered the storm.Buttigieg admitted that South Bend’s police force remains disproportionally white “because I couldn’t get it done”.He added: “I am determined to bring about a day when a white person and a black person driving a vehicle feels the exact same thing when they see a policeman – a feeling of safety not fear.”Gun violence as a debating issue. Swalwell said he would ban and then buy back every assault weapon in America; Buttigieg, leaning on his status as the only war veteran on stage, said that guns were “tearing us apart”; Harris promised to take executive action to ban the importation of assault rifles. 5\. A bad night for …Joe Biden, obviously.Bernie Sanders, who looked as though he were stuck in the same old groove. And the also-rans. There have been plenty of moments over these past two nights when nobody seemed to be able to remember why certain individuals were even on stage. Were they gatecrashers?That thought came forcefully on Thursday night with the two jokers in the pack – Andrew Yang, a former tech entrepreneur, and Marianne Williamson, a bestselling author of self-help healing books (typical title: 21 Spiritual Lessons for Surrendering Your Weight Forever). What was Williamson doing talking about love being the way to defeat Trump?