The Democratic Party convened late on Monday night for a virtual convention that will officially nominate Joe Biden as the US presidential candidate, with less than 80 days until voting begins. Polls show that Mr Biden has built a strong lead in nearly every battleground state that Republican President Donald Trump won narrowly in 2016. Mr Trump's approval numbers have fallen amid the coronavirus pandemic and rising unemployment figures. For the first time in a decade, the Democrats' hopes of retaking the Senate – and full control of Congress – are within sight. But as Democrats nationwide gather online this week, many are wary of trusting the polling numbers that show Mr Biden's lead. The party has learnt from mistakes made in 2016, when polling also placed former Democratic presidential candidate Hillary Clinton as the front-runner. Some Democrats fear victory could slip from their fingers again. There are no crowds, no fuss and no balloons – the usual backdrop to the carefully orchestrated convention. The event is being held in Milwaukee, Wisconsin, but the majority of the speeches are being delivered remotely. The convention will run through Thursday, with much of it having been taped earlier. Mr Biden will accept his presidential nomination from his home state of Delaware. Closing off the first night was former first lady Michelle Obama, who served as a reminder of the Democratic party’s better days under the Obama-Biden presidency. Wrought by the political turmoil brought on by the Trump administration, the Obama legacy is fondly remembered by many Democrats and other Americans as an emblem of stable government. The election will provide an opportunity to finish that work, said Ms Obama. The former first lady spoke about the traits of a good leader, citing empathy, the importance of listening and having a strong moral foundation. "Donald Trump is the wrong president for our country," she said. “He is clearly in over his head." Speaking about the racial tensions that emerged this summer in the US, Ms Obama said "sadly this is the America that is on display for the next generation." "That's not just disappointing, it's downright infuriating," she said. Bernie Sanders, who dropped out of the presidential race in April, also backed Mr Biden. “This election is the most important in the modern history of this country,” he said Mr Sanders said the "unthinkable" is now normal in US. He said the country was struggling with a public health crisis, an economic collapse, systemic racism and the “enormous” threat of climate change. The approval of Mr Sanders is considered to be key to bringing in the progressive arm of the party as the self-professed democratic socialist has maintained popularity among young voters and left-of-centre supporters. Mr Sanders' ideas on single-payer health care, tuition-free college and remaking the economy to battle climate change are now part of the mainstream debate. "Many of the ideas we fought for, that just a few years ago were considered radical, are now mainstream," he said. But the progressive movement is still far from the driving force of the Democratic Party. Mr Biden won the primary largely as a centrist who relied heavily on his decades of experience working within the Washington system, not promising to tear it down. His running mate, California Senator Kamala Harris, is similarly aligned with the Democrats’ traditional establishment. “They [progressives] are going to get a seat at the table but Joe Biden is very much a creature of Washington,” said Colin Strother, a Democratic strategist. “They want a revolution. That’s not how Washington works.” Mr Trump has planned visits this week to Minnesota, Wisconsin, Arizona and Pennsylvania, all competitive states. Democratic officials, activists and voters fear that Mr Trump will make voting as difficult as possible and should he lose the vote, some worry he will not accept the outcome. Former president Barack Obama has also sounded the alarm recently, saying on Twitter the Trump administration is "more concerned with suppressing the vote than suppressing a virus". Eight of 10 Democrats are concerned about voter suppression, a Reuters-Ipsos poll said in late July. Mr Trump has railed against voting by mail for months, claiming without evidence it will lead to fraud. A spokesman for the Trump campaign said the president wants a "free and fair" election. Some Democrats also fret that the race has become overly focused on his handling of the pandemic. That has so far worked in Mr Biden's favour, but it has also left him vulnerable to a single-topic campaign that could be hindered by any sudden shift in the country's fortunes, such as lowering case numbers, breakthrough in vaccine development or significant economic improvement.