Joe Biden was hoping to deal a debilitating blow to leftist rival Bernie Sanders on Tuesday as six states including crucial Michigan began voting in the Democratic presidential primaries.
A week after his startling turnaround in the "Super Tuesday" primaries, the centrist former vice president in the Obama administration is hoping another big night could make him invincible as the Democrats pick a challenger to face President Donald Trump in November.
Sanders has acknowledged that Michigan is critical and like Biden has spent days barnstorming the state, one of three where Trump in 2016 pulled off narrow upsets that won him the White House.
Biden and Sanders are both septuagenarian veterans of the Senate but are running starkly different campaigns. Biden, who enjoys a sizable lead in polls, advocates a traditional Democratic platform of liberal legislative reforms while Sanders is urging a roots-up socialist revolution.
Artist and designer Cecilia Covington, 61, was the first person to vote in Precinct 123 in downtown Detroit, braving the darkness and a cold drizzle as she arrived at Chrysler Elementary School well before it opened as a polling station at 11:00.
Covington has been a Biden fan from the start of his campaign, which began with two crushing defeats before his convincing win in South Carolina.
"When he wasn't doing well in the polls I was really concerned," she admitted. "But when he won the South Carolina primary I put my confidence back in him."
"We've got to get '45' out of office," she said, referring to the current president.
The primaries come with the US, like much of the world, roiled by the coronavirus epidemic that has infected almost 800 people across the country and killed 26.
Washington state, which has borne the brunt of the crisis, votes entirely by mail.
The Centers for Disease Control and Prevention has offered guidance on cleaning voting machines and other technology for the other states voting. Among them, only Missouri had confirmed a case by Tuesday according to Johns Hopkins University.
Idaho, Mississippi, and North Dakota were also voting.
But the day's top prize is Michigan, with its large delegate haul, status as a swing state and demographics that mirror the United States, with rural, urban and suburban bases and a sizable minority community.
Biden - the faithful deputy for eight years to Barack Obama, the first black president - has been surging with strong backing from African Americans.
Ahead of the Michigan vote, he picked up endorsements from the Senate's two black Democrats, Kamala Harris and Cory Booker, the latest failed presidential candidates to rally behind Biden.
Sanders has won the backing of civil rights leader Jesse Jackson, who ran for president in 1984 and 1988, and has highlighted Biden's support for free-trade deals to win over Michigan's disaffected blue-collar voters, many of whom ditched the Democrats for Trump four years ago.
"We are in a crisis in America, not only in the need to defeat Donald Trump, the most dangerous president in modern American history, but to take on the greed and corruption of corporate elite," Sanders said in an ABC interview.
"That is what our campaign is about. It's very different than Joe's."
Biden has also courted blue-collar workers, highlighting his own hard-knock childhood in Pennsylvania and Delaware and on Tuesday opening the primary day by meeting workers at a Fiat Chrysler plant.
"Wall Street didn't build America, you built America," Biden told a rally in Detroit. "Unions built the middle class."
Biden won 10 out of 14 states that voted on Super Tuesday and holds a narrow lead in delegates to pick the nominee, although Sanders carried the most populous state of California.
Trump has sought to portray Sanders as the victim of a conniving Democratic establishment, a narrative that some experts believe could depress turnout and benefit Republicans.
But Sanders supporter Frank Anderson, a 24-year-old software engineer, said he was optimistic for a victory, noting how Sanders triumphed in the 2016 Michigan primary over Hillary Clinton.
"They had counted us out then, so I'm hopeful for today," Anderson said.
"His consistency over the last 40 years, his policies aimed at, you know, restoring the middle class, and really everything he's been fighting for his entire life, I stand with," he said.
Regardless of the outcome, both Biden and Sanders plan to head Tuesday evening to another Rust Belt state, Ohio, which votes one week later.
The March 17 primary could prove even more decisive with three other major states also voting - Arizona, Florida and Illinois.