A collapse in support among Arab-Americans and young liberal voters over Gaza has concerned Democrat strategists, who believe it could harm Mr Biden in November’s presidential race.
Michigan, which has one of the highest state Muslim populations in the US, is also a key battleground for Mr Biden that he won by a margin of less than three percentage points in 2020.
The Biden campaign made no mention of the wave of “uncommitted” votes following Tuesday’s result, instead hailing “Michigan’s diverse coalition”.
In a statement, Mr Biden said: “I want to thank every Michigander who made their voice heard today. Exercising the right to vote and participating in our democracy is what makes America great.
“Four years ago, it was Michigan’s diverse coalition that came together to reject Donald Trump’s MAGA extremism and sent me and Kamala to the White House. Because of Michiganders, we’ve been able to work hand in hand with Governor Whitmer and the incredible Democratic leaders in Michigan’s congressional delegation to deliver enormous progress.”
Another crushing defeat for Haley
In the Republican primary, early results suggested Mr Trump had won around 65 per cent of the vote, to Ms Haley’s 31 per cent.
Ms Haley’s defeat in Michigan – which was predicted by opinion polls – comes as she struggles to maintain credibility in the Republican primary race.
The former UN ambassador has lost every state vote so far to Mr Trump, including her home state of South Carolina on Saturday.
Despite heavy losses of up to 20 percentage points and the decision of other Trump rivals to suspend their campaigns, Ms Haley has pledged to stay in the contest to give Republican voters an “alternative”.
“They have the right to a real choice, not a Soviet-style election with only one candidate,” she said on Saturday, adding: “I have a duty to give them that choice.”