There wasn't much doubt that President Biden and former President Trump would romp to victories in the Michigan primaries Tuesday. But Biden's win in particular revealed his vulnerability in a crucial swing state that could decide the presidency in November.

Why it matters: Arab American and young voters — key to Biden winning Michigan in 2020 — turned out by the tens of thousands on Tuesday to vote ... not for Biden, but for "uncommitted" in the Democratic primary.

• The protest vote, driven by anger over Biden's handling of the Israel-Hamas war, had drawn more than 100,000 supporters with 98.5% of the ballots counted — several times more than organizers expected.
• That took some of the glow from a victory in which Biden got more than 80% of the vote, and confirmed that Biden has some serious persuading to do between now and November.
• "We need more than just nice words and hope. We need a permanent ceasefire" in Gaza, Layla Elabed, campaign manager for Listen to Michigan, told CNN. The group was behind the "uncommitted" vote effort.

Other takeaways from Michigan:

1. Biden has other problems, too.

• Another jolt for the president's campaign Tuesday: A jarring enthusiasm gap between the Democratic and Republican primaries.
• Nearly 40% more people voted in the Republican primary than in the Democratic contest — despite the protest campaign that aided turnout on the Democratic side.
• Trump, who once again defeated former UN ambassador Nikki Haley, got more votes on the GOP side than the total number of votes cast in the Democratic primary between Biden, "uncommitted" and two other candidates.

2. It wasn't all good news for Trump.

• That surge in GOP voters was driven in part by about 27% of Republicans voting for Haley, whose support continues to be not nearly enough to win the Republican nomination — but enough to show that a sizable chunk of the GOP may never be on board with Trump.
• Haley's campaign might not last beyond Super Tuesday next week, when Trump is expected to score hundreds of delegates and put a virtual lock on the GOP nomination as 16 states hold contests.
• But Haley's level of support suggests that many of her backers may stay home in November — or even vote for Biden, if Trump is on the ballot.
• That could be a big factor in Michigan and the half-dozen or so other swing states likely to decide the election.

3. Not a great night for Dean Phillips.

• Phillips, a Minnesota Democrat, gave up his House seat last October to run for president. He became a frequent critic of the 81-year-old Biden, saying he was too old to run again and should make way for a new generation of leadership.
• Phillips, 55, also said Biden should have competition in the Democratic primary.
• It hasn't quite worked out: Phillips' campaign has never gained traction, and he's faced intense criticism from Democrats who've accused him of helping Trump as the former president prepares for a likely rematch against Biden.
• Michigan's Democratic primary felt like the end of the road. Phillips appeared to be headed to a fourth-place finish — behind Biden, "uncommitted," and Marianne Williamson, an author and spiritual leader.

Editor's note: This story has been updated with the latest "uncommitted" vote tally.