by Hannah Thomas-Peter, US correspondent

Over the weekend San Francisco briefly transformed into the centre of the Democratic Party's universe.

Alongside thousands of delegates, I watched no fewer than 14 presidential candidates speaking at the state convention there.

It amounted to a raucous early audition for the presidential nomination in front of some of the most progressive party members in the country.

Not everyone turned up.


Joe Biden was notably absent, for example.

But the event was still a rare chance to see the candidates side by side, just as the primary race begins in earnest.

Image: New Jersey Senator Corey Booker probably gave the best speech

New Jersey Senator Corey Booker probably gave the best speech - a soaring sermon on how Democrats must make the 2020 election a referendum on the character and soul of a nation.

Mr Booker is not doing well in the polls but he has the capacity to raise goose bumps when he hits those notes - a skill few others in the field possess.

The audience liked it a lot, although maybe because they were hungry for the sentiment and not for the man, who gravitates too easily to the cameras and has the air of a big fish in a small pond.

Jay Inslee did well too - he has a cogent, radical plan to combat climate change and transform America in the process.

It has scored top marks with activists and young voters in particular, many of whom demand nothing less than the greatest collective mobilisation since World War II.

In the Golden State, which has been ravaged by wildfires, mudslides and drought, it is a prerequisite that candidates acknowledge the existential threat and demonstrate they've thought clearly about a response.

But Mr Inslee has a major optics problem.

Somehow he looks and sounds like a Republican. Don't ask me why. He just does.

Image: Bernie Sanders speeches have largely been the same as his 2016 campaign

Bernie Sanders, on the other hand, definitely does not.

Although to my ear he has a different, slow burn, disadvantage.

Suddenly, because everyone else has adopted the policies he pioneered in 2016, his speech sounds, well, like a rehashed stump speech.

Has Bernie's moment gone?

Maybe.

Maybe Beto O'Rourke's has too.

Let's see who else….

Tulsi Gabbard. Yawn.

This is unfair.

Image: Bernie Sanders moment may have gone

I mean she's yawn in performance, not yawn in substance - a veteran, steely, able to reclaim patriotism for the left, full of potential .. and yet somehow locked inside herself.

Her team had better find the key, and quickly, although it may already be too late.

Mayor Pete Buttiegieg; confident, poised, funny, but lacking a certain kind of sizzle at this event, which is a shame.

To me, the multi-lingual gay veteran millennial mayor of an industrial Midwest town is by far the most interesting and dangerous candidate in the field.

Perhaps he felt a long way from home. The California Democrats are a rowdy bunch, after all.

Image: Tulsi Gabbard? Yawn, says Sky's Hannah Thomas-Peter

They showed poor John Delaney no mercy when he made the egregious error of claiming that Medicare for all was bad policy (someone fire the chief of staff, I mean honestly who would do this in California of all places).

Anyway the boos lasted for the entire last half of his seven minute speech, at which point loud music played him off, like an actor accepting an Oscar who got carried away.

It was excruciating.

But who, I hear you ask, who was it who electrified the room?

Elizabeth Warren.

I know!

The 69-year-old Massachusetts senator received a rapturous reception, eclipsing even that of Kamala Harris, a daughter of California.

Image: Elizabeth Warren electrified the audience

I thought Ms Harris went a bit fight-them-in-the-streets, rather mistaking her home state delegates' rowdiness for anti-Trump blood lust.

It didn't quite get there.

Ms Warren on the other hand, walked on to the stage as if she were very purposefully going to the shops for a pint of milk.

With almost no sense of theatre, she spoke earnestly of "bold structural change" to the nation.

There is nothing catchy about how she makes her arguments around remedying economic injustice.

Her social media hashtag #shehasaplanforthat is almost wilfully uninspiring.

But the crowd went wild.

Can it be true that Ms Warren is catching on?

Could she ever beat Donald Trump, who once mocked her native American heritage by calling her "Pocahontas"?

It is hard to imagine.

With almost no sense of theatre, [Elizabeth Warren] spoke earnestly of 'bold structural change" to the nation. Her social media hashtag #shehasaplanforthat is almost wilfully uninspiring. But the crowd went wild.

But if Ms Warren continues to inspire California delegates she's on the right path.

The state usually holds its primary late in the season, by which point the party's nominee is often a foregone conclusion.

In 2020, it will be on 3 March, otherwise known as Super Tuesday - a day with outsize influence on who edges to the front of the pack.

In a such a crowded field with an anything can happen vibe, Ms Warren should not be underestimated.

I just can't work out why yet.

Sky Views is a series of comment pieces by Sky News editors and correspondents, published every morning.

Previously on Sky Views: Martha Kelner - Fans' unity has enormous power to drown out hatred and bile