The Democratic nominee in 2020 will be Joe Biden, Elizabeth Warren or Bernie Sanders. Everyone else is irrelevant.

Don’t get me wrong. The entire field is impressive. Every candidate in last week’s debate would make a far better president than the current inhabitant of the Oval Office.

But let’s get real. Biden, Warren, and Sanders each continue to garner around 20% in the polls while all others are in the single-digit doldrums. The frontrunners also have the money and the organization.

Yet eight Democrats have already qualified for the 20 November debate in the Atlanta area, including the senators Kamala Harris and Cory Booker, Mayor Pete Buttigieg, the entrepreneur Andrew Yang and the billionaire Tom Steyer.

By 13 November, the last date for meeting the Democratic National Committee criteria, I wouldn’t be surprised if the former representative Beto O’Rourke, Senator Amy Klobuchar, the former housing secretary Juliían Castro and Representative Tulsi Gabbard were also on board.

Trump has never stopped campaigning. His incendiary lies continue to reverberate

This is nuts. What’s the point of another three-hour marathon? With so many candidates, all we get are soundbites, gotchas and one-liners.

Perhaps someone in the second tier will be picked for vice-president or will end up in the next president’s cabinet, or their exposure will help win a seat in the House or Senate, or a governorship. But this is not enough reason to continue this overly extended beauty contest.

Support must consolidate soon. Time is wasting. Take out the holidays and by 20 November the caucuses and primaries will be only weeks away. The Iowa caucuses are on 3 February.

If we were going into a normal general election, the huge field of wannabes wouldn’t be a problem. But this won’t be a normal election. These are not normal times. If you hadn’t noticed, Donald Trump is not a normal president.

Impeachment is sucking huge amounts of oxygen from the political air, and will continue to do so for months.

Meanwhile, Trump’s campaign is in full gear. His fundraising machinery – the Republican National Committee, Super Pacs, his official campaign – has raised more than $736m. That’s more than any presidential candidate at this point in a campaign.

Trump has never stopped campaigning. His incendiary lies continue to reverberate through Fox News, rightwing radio and social media.

The larger the Democratic field, the harder it is for any single candidate or message to break through the cacophony.

At the same time, second-tier candidates are under growing pressure to take pot shots at the front runners – planting negative stories, poking holes in their plans, building themselves up at their expense. This may be rational for them but it’s irrational for the Democrats as a whole.

The old saw that a nominee benefits from having to respond to many other candidates doesn’t apply to this election.

If you thought the 'swift boating' of John Kerry in 2004 was outrageous, wait until Trump launches his aircraft carriers

Trump will not be debating subtle differences between Medicare for All and Medicare for Those Who Want It. He will accuse the Democrat of being a communist, and worse.

It’s time to for Democrats to hunker down. The debaters on 20 November should be Biden, Warren and Sanders.

Warren and Sanders should be given a chance to fully explain how their ideas differ. Biden needs to explain why he believes America should return to the politics we had before Trump, when that politics led to Trump.

All three should have ample time to describe how they’d win over working-class Americans who have been shafted for 40 years.

They also need room to discuss how they’ll create a multi-racial, multi-ethnic coalition to take power back for the bottom 90%, and how they’ll get big money out of politics and restore our democracy.

And they need to address how they’ll take on Trump’s malicious lies and anything-goes tactics. If you thought George W Bush’s “swift boating” of John Kerry in 2004 was outrageous, wait until Trump launches his aircraft carriers.

Americans deserve a full opportunity to assess these three candidates and decide which should take on Trump. It’s not too late for the DNC to tighten the rules for who gets to debate next.

The stakes could not be higher. This will be the most important election in modern American history. We – not just Democrats but all Americans – cannot afford to blow it.