Joe Biden has cemented his position as front-runner in the Democratic race to take on President Donald Trump in November’s White House election.
The former vice-president won Michigan, the biggest prize of primary voting on Tuesday, extending his lead over main rival Senator Bernie Sanders.
Five other states – Washington, Missouri, Mississippi, Idaho and North Dakota – voted on Tuesday.
Mr Biden also swept aside Mr Sanders in Missouri, Mississippi and Idaho.
It was unclear if Mr Sanders would fight on until the party convention in July.
The Democrats’ next big election milestone is in a week’s time when 577 delegates are up for grabs.
To secure the nomination, a candidate needs the support of 1,991 delegates. Before Tuesday’s vote, Mr Biden had 648 to Mr Sanders’ 563.
The former vice-president had lagged behind his Democratic rivals in early voting states, but rebounded after big wins on Super Tuesday and endorsements from several former nomination rivals.