Democratic presidential candidate Joe Biden has steamrolled rival Bernie Sanders in primary elections in Florida and Illinois, US media project.
Accelerating his momentum in the race, the former US vice-president led Mr Sanders in both states with over 60% of the vote.
Arizona was also voting on Tuesday, though its polls have not yet closed.
Mr Biden is the favourite to become the Democratic candidate who will face President Donald Trump in November.
The former US vice-president is hoping to build an unassailable lead in the race for the Democratic leadership after scoring victories in 16 of the last 21 state contests.
According to opinion polling, most Florida voters said electability was a priority for them.
About three in four 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.
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 the traditional battleground state by 1.2 percentage points in the 2016 presidential election.
Ohio was also due to hold a primary on Tuesday, but it cancelled the vote because of the nationwide coronavirus outbreak.
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 has urged the remaining primary states not to postpone their voting.
Party grandees are encouraging the states to extend postal and early voting to reduce public exposure to the respiratory illness.