BBC.COM-Democratic presidential candidate Joe Biden has steamrolled rival Bernie Sanders in primary elections in Florida, Illinois and Arizona.
Accelerating his momentum in the race, the former US vice-president made a clean sweep in all three states.
Mr Biden appealed for support directly to Sanders supporters.
With his hat-trick, Mr Biden took another big stride towards becoming the Democratic candidate who will face President Donald Trump in November.
What are the results so far?
With most Florida precincts reporting, Mr Biden led Mr Sanders by nearly 62% to about 23%, according to the Associated Press news agency.
In Illinois, with most precincts reporting, Mr Biden led the Vermont senator by 59% to 36%.
According to partial results from Arizona, Mr Biden had a double-digit lead on Mr Sanders.
In that south-western state, Mr Biden led among white voters by 51% to 32%. Hispanic voters were more equally divided between Mr Biden (45%) and Mr Sanders (44%).
Florida was the biggest prize of the night, awarding 219 of the 1,991 delegates needed to secure the Democratic presidential nomination.
Mr Trump won that traditional battleground state by 1.2 percentage points in the 2016 presidential election.
On the eve of Tuesday’s vote, Mr Biden was hoping to build on his victories in 16 of the last 21 state contests.
The former US vice-president’s triumph last month in South Carolina – his first ever primary win over three campaigns for president – resuscitated his faltering campaign.
What issues mattered to voters on Tuesday?
According to opinion polling, most voters said electability was a priority for them.
About three in four Florida voters said Mr Biden would have a better chance of beating Mr Trump, a Republican. Just one in five said the same of Mr Sanders.
Older voters were more likely to say they supported Mr Biden.
Nearly half of Florida’s voters said Mr Sanders’ stances were too liberal.
How did the two candidates react?
In a webcam speech from his home in Wilmington, Delaware, to comply with US anti-coronavirus advice against public gatherings, Mr Biden appealed to Mr Sanders’ passionate supporters.
He said: “Let me say, especially to the young voters who have been inspired by Senator Sanders, I hear you, I know what’s at stake, I know what we have to do.”
But he focused largely on the outbreak sweeping the US, striking a unifying tone as he said: “The coronavirus doesn’t care if you’re a Democrat or a Republican… we’re all in this together.”
Mr Sanders hosted an online address from Washington DC, but he did not drop any hints about the future of his campaign.
He instead talked about the coronavirus crisis, outlining proposals to address the pandemic, which he said would cost some $2tn.
Game over for Bernie Sanders?
Democrats in three states have just cemented the presidential nomination for Joe Biden.
Bernie Sanders was soundly defeated in Illinois and Arizona and routed in Florida, where in one county he finished third behind Michael Bloomberg, who dropped out weeks ago.
He will fall even further behind in the national convention delegate count, as the primary season appears to be heading towards suspended animation, with multiple states delaying their contests until June.
Mr Sanders should have a long think about how long he wants to stay in this fight, even if he does have more than enough financial resources to carry on.
He is going to face growing calls from Democrats to gracefully bow out – something he did not do until the eve of the convention four years ago, much to the consternation of many Hillary Clinton supporters.
The bottom line for Mr Sanders may be evaluating what’s best for the movement he created.
Will staying in the race give him a continuing platform to talk about his issues and buy him time for a potential comeback?
Or will hanging around only increase the chances that he is relegated to an electoral afterthought?
What about President Trump?
Also on Tuesday night, the US president officially clinched the Republican party nomination with a win in the Illinois primary.
His victory had been a foregone conclusion in a contest where he has faced only nominal opposition from a former Massachusetts Governor, Bill Weld.
Illinois’ delegates drove Mr Trump over the 1,276-delegate threshold required to become the party’s standard-bearer.
Republican National Committee Chairwoman Ronna McDaniel congratulated the president on Twitter for “officially becoming the presumptive Republican nominee”.
How else is the coronavirus affecting election season?
Ohio was also due to hold a primary on Tuesday, but it cancelled the vote hours before polls were due to open, putting it off till June.
Voters in the three states that did head to polling stations on Tuesday encountered hand sanitiser dispensers and workers in surgical gloves.
Several other states have postponed their Democratic presidential primaries, including Georgia, Louisiana, Maryland and Kentucky.
The Democratic National Committee blasted Ohio for sowing “chaos and confusion” and urged remaining primary states not to follow suit.
But Puerto Rico, which is scheduled to hold the next Democratic primary on 29 March, is also planning to reschedule.
Party grandees are encouraging states and territories instead to extend postal and early voting to reduce public exposure to the virus.
Who’s getting Secret Service protection?
On Tuesday, the US Secret Service said it would this week begin providing full protection for Mr Biden. His codename will be Celtic, the same as when he was vice-president.
Mr Biden requested the security detail after being repeatedly accosted by protesters on the campaign trail.
Two protesters rushed a stage in Los Angeles earlier this month and came within a stride of the candidate as he gave a victory speech.
Mr Sanders has not made a request for Secret Service protection.