Bernie Sanders 2020: veteran Left-winger must face crowded field of copycats to gain Democratic nomination

So, Bernie is in. Four years after his remarkable rise from relative political obscurity to almost upsetting Hillary Clinton’s march to the Democratic nomination, he is back for another go.

His strengths as a 2020 presidential candidate come from what happened during that first try. He has a network of political activists embedded in key states who have been pushing his case since he came up short.

He has name recognition and a clear political identity, something many of his rivals in a packed field of more than a dozen likely candidates will need to carve out in the coming months.

Mr Sanders also has proven heft when it comes to fund raising. He picked up more than $100 million (£77 million) from donors who gave less than $200 each during his last presidential bid – numbers that aren’t to be sniffed at.

The young Democrat voters drawn to his Left-wing policies also appear to still be drifting that way. A Gallup poll in 2016 found Democrats felt more positively about socialism than capitalism.

But there is one big challenge for Mr Sanders – this time he is not alone. At least half a dozen candidates are looking to ride the same progressive wave that he surfed so successfully in 2016.

That much is clear when you look at the policies with which he is most clearly identified. Medicare for all - a proposal to give every American government-paid healthcare - has been one of his big rallying cries for years.

He introduced a bill proposing it in 2017.  But four other presidential rivals – the senators Elizabeth Warren, Kirsten Gillibrand, Cory Booker and Kamala Harris – all co-signed the bill and are backing versions of the same idea.

In 2016, Mr Sanders called climate change “the single greatest threat facing our planet”. But the Green New Deal he wants adopted is being pushed by others too, including Ms Harris and Ms Gillibrand.

His vocal attacks on Wall Street and calls for free college tuition helped set him apart from Mrs Clinton in 2016. Yet this time round Ms Warren, perhaps the candidate who most overlaps with him in terms of policy, is hammering away at both issues.

Plus another feature of Mr Sanders’ last campaign – his reluctance to take corporate donations to fund his bid for the White House – is now commonplace among the 2020 pack.

There are weaknesses too. In the #MeToo world, allegations of sexual harassment from his 2016 campaign, which led to Mr Sanders issuing an apology, could put off some voters.

At 77, Mr Sanders is five years older than Donald Trump, and this will be focused on, as will his electability at a time when the Democrat base appears to prioritise finding a candidate who can beat the current US president above other qualities.

Mr Sanders will also be hoping to improve his standing with African-American voters, a demographic that preferred Mrs Clinton over him last time round.

In 2016, Mr Sanders was the change candidate. Despite the historic nature of Mrs Clinton’s candidacy, her perception as the embodiment of the establishment helped fuel his campaign.

In 2020, it will be much harder to play that card. Among Mr Sanders’ rivals are people seeking to be the first black woman, gay man and Latino candidate to be US president.

Early polls suggest Mr Sanders is well positioned - he tends to come second after Joe Biden, the former US vice president. And last time he won more than 13 million votes in the primaries, which is no mean feat.

But 2020 is not 2016. This is not a two-horse race but a free-for-all, with plenty of candidates looking to occupy turf long staked out by Mr Sanders.

He is no longer the only progressive in town.