Democratic debate - winners and losers : Kamala Harris goes after Joe Biden over race comments as healthcare, gun control and the migrant crisis dominate event

While the candidates prepare for tonight's debate, the US Supreme Court has blocked the Trump administration from adding the controversial citizenship question to the 2020 census - a topic that may come up at tonight's debate.

Read more here: 

Popular Congresswoman Alexandria Ocasio-Cortez has given her take on the first debate, saying three candidates in particular stood out for her:

From our reporter Clark Mindock in Miami: 

According to an instant poll released by Drudge Report early Thursday morning, Tulsi Gabbard had the biggest win of the first night, with nearly 45 per cent of the vote.

The current Democratic frontrunner, Joe Biden, will take to the stage in Miami tonight, but despite his strong lead, he wasn't mentioned once in the first debate. There had been expectations his rivals would criticise him during the Wednesday showdown, but the discussions didn't venture into directly slamming other candidates.

Another of the big names at tonight's debate is Bernie Sanders, who delighted gaming fans yesterday by launching his own Twitch account. 

The senator is expected to do a live stream on the site before and after the debate. 

One of the big dividers at last night's debate - and likely to be again tonight - was healthcare. 

Amy Klobuchar attacked Medicare for All, which candidates like Elizabeth and Bernie Sanders of Vermont have embraced. John Delaney also chipped in, getting a strong response from the audience for saying: "I think we should be the party that keeps what's working and fixes what's broken."

Here's what our US voices editor Holly Baxter had to say about last night's debate: 

While huge numbers weren't expected, Wednesday's debate drew more than 15m viewers on NBC, MSNBC and Telemundo, NYT reporter Michael M Grynbaum reports. 

The number is much lower than the 24m viewers that watched Donald Trump's first debate in August 2015. 

Thursday's debate is expected to draw a similar viewership. 

MIAMI — In downtown Miami right now, things are pretty quiet, but we have about five hours until the second debate is set to start.

Earlier today, I saw Bernie Sanders and Beto O'Rourke in Homestead — a Florida city about a 50 minute drive from Miami. Tulsi Gabbard was expected to be there a bit later, too.

They were there to take a look at a child migrant camp down there, which has ballooned into a major issue in the Democratic primary amid reports of squalid conditions at detention centers, and the tragic deaths of two migrants crossing the Rio Grande who were captured in a heartbreaking photo.

Mr Sanders and Mr O'Rourke both climbed up a portable ladder that the volunteers there — "witnesses" they call themselves — have set up so they can peer over a fence into the compound.

It was incredibly hot, and both candidates sweat quite a bit as they looked over at the children who, inside, were wearing orange hats. Mr O'Rourke even yelled a few messages in Spanish alongside the "witnesses" who have been doing so to let the kids know they are not alone for 37 straight days now.

Other candidates who plan on or have gone there: Elizabeth Warren (yesterday), and Pete Buttigieg) tomorrow. Bill de Blasio was there this morning when I arrived, but I didn't catch much of his interactions.