Elizabeth Warren, Barnie Sanders and Kamala Harris.

Edward Hardy, The Independent

Senator Bernie Sanders’ presidential campaign has stepped up attacks on his Democratic rivals this week as the party’s 2020 presidential primary field narrows, setting its sights, in particular, on Senator Elizabeth Warren and Senator Kamala Harris.

The first shot fired came from Jeff Weaver, a senior adviser to the Sanders campaign, who dismissed the threat Warren posed by stating that they are not “competing for the same pool of voters” and that Sanders’ “base is much more diverse”.

The second hit came from Sanders himself, when he took to Twitter to declare that “I don’t go to the Hamptons to raise money from billionaires” hours after Harris held a fundraiser in the popular resort.

The third attack came from activist Susan Sarandon, who praised Sanders by stating that “he is not someone who used to be a Republican” – something many saw as an indirect criticism of Warren, who was a registered Republican in the mid-1990s.

The increase in attacks clearly reveals that Sanders and his campaign team are concerned at the recent polls showing he’s in a four-way battle for the Democratic nomination with Joe Biden, Elizabeth Warren and Kamala Harris. His campaign has shifted strategy accordingly, as the people around him focus on criticising – directly and indirectly – the most threatening opponents in the primary contest.

Elizabeth Warren is arguably Sanders’ biggest threat as she recently leapfrogged him in the polls and seems to be extending her lead. Furthermore, unlike other candidates, Sanders can’t attack Warren for her lack of clear policy positions, as she has laid out the most comprehensive policy platform of any Democratic candidate, releasing detailed proposals on an almost weekly basis.

Kamala Harris poses a concern for a slightly different reason, as, during the first debate, she catapulted herself into top tier contention with an eviscerating attack on Joe Biden, positioning herself as a new face against an old establishment. With Bernie Sanders’ long track record in politics – which opens him up to potentially greater scrutiny – he has reason to be legitimately concerned that when he stands on a debate stage, in a smaller field, with Harris, she will turn her attention to highlighting and critiquing any missteps he has made throughout his career.

However, this descent into Democratic infighting could pose a significant problem for the party as it heads into the 2020 contest with Donald Trump. While you can expect to see the candidates attack one another in an attempt to differentiate themselves throughout any party’s presidential primary, this is no ordinary election.

There are plenty of criticisms for the Democrats to level against Donald Trump, from his handling of the economy – which has left experts fearing another recession is imminent – to his immigration policy – which has resulted in the family separation policy and detention centres filled with migrants in cages. But Democrats have been disproportionately focused on infighting over the last few weeks, which is exactly what voters feared would happen when so many candidates put themselves forward for the 2020 candidacy originally.

Democrats need to be careful that they don’t do Trump’s job for him; that they don’t throw attacks out there that irrevocably damage whoever is the eventual nominee before they even get the chance to go toe to toe with Trump. The presidential candidates can explain why they are different to their opponents and why they would be a stronger candidate in the election. That’s fine. However, they also need to emphasise where they are united – from environmental policies to expanding access to affordable healthcare – in order to build a movement that will help them regain control of the White House in 2020.

If Democrats continue to spend more time tearing chunks out of each other than challenging the current occupant of the Oval Office, they will lose the 2020 race, just like they lost the 2016 election.