But the risks are enormous for Biden if even a small segment of the coalition that powered him to the White House stays home or chooses a third-party candidate instead.

The very last votes of the Democratic primary will be cast in Guam and the U.S. Virgin Islands on Saturday, and Biden will soon officially become the nominee. He cruised to the nomination, even compared to past vulnerable incumbents like Jimmy Carter and George H. W. Bush who were ousted after one term. But there’s a stubborn, nearly 10 percent slice of the Democratic electorate that keeps voting “uncommitted,” including in New Jersey (9 percent) and New Mexico (10 percent) on Tuesday.

The primaries also presented potential warning signs for Trump. But Biden is currently trailing in the general election. And while Nikki Haley kept garnering votes in the once-solidly-Republican suburbs well after she ended her campaign — a weakness for Trump in places that have fled his party — many of Biden’s primary holdouts came from his electoral base.

Here are three lessons from the protest votes in the Democratic presidential primaries:

Biden might have the most work do with Arab American voters

The “uncommitted” protest vote was first organized in Michigan, with Arab American and Muslim voters seeking to send a message to Biden over his response to the Israel-Hamas war.

Those voters, in Michigan and elsewhere, offered up perhaps the most significant rejection of Biden in the Democratic primary. “Uncommitted” got more votes than the incumbent in the Michigan cities of Dearborn and Hamtramck in February, en route to 13 percent overall in the state, kicking off a wave of efforts to organize protest votes across the country.

A week later, “uncommitted” got 19 percent in Minnesota, driven by strong performances in the Twin Cities. Trump even suggested he could put the state in play this year after losing it by more than seven points in 2020, although Democrats and even many Republicans have been skeptical of that claim.

Other primaries largely haven’t reflected enough of an Arab American voting base to show a continuation of, or a variance from, the Michigan and Minnesota results. But recent polling has suggested support for Biden among Arab American voters has plummeted compared to 2020.

Trump may not be in a position to pick up that support. But Arab American and Muslim voters staying on the sidelines in November could still be a problem for Biden come November, particularly in a key swing state like Michigan.

Organized college students expressed their displeasure

As activism over the war spread across college campuses, the “uncommitted” vote repeatedly put up notable shares in college and university towns. That reflected the strength of organizing among student activists who mobilized around the “uncommitted” cause to show opposition to Biden’s handling of the war in Gaza.

In Michigan, “uncommitted” got 17 percent of the vote in Washtenaw County, driven by voters in Ann Arbor and Ypsilanti, respectively homes to the University of Michigan and Eastern Michigan University, including outright winning one precinct in each.

In Wisconsin, a handful of precincts in Madison around the University of Wisconsin saw at least 40 percent of voters cast their ballots for “uninstructed.” In Washington state, the “uncommitted” vote won two delegates to the Democratic National Convention after it cleared 15 percent of the vote in the state’s 7th Congressional District; more than a dozen precincts, mostly those adjacent to the University of Washington and Seattle University, saw at least a third of voters vote uncommitted.

The trend played out even when “uncommitted” wasn’t on the ballot. In Pennsylvania, where there was no “uncommitted” option, organizers encouraged protesters to cast write-in votes instead. In Philadelphia and Pittsburgh, the precincts with the highest rates of write-in votes were those close by various university campuses.

‘Uncommitted’ didn’t spread outside of its base, but other challenges remain

Biden’s campaign has also faced questions about whether he can maintain support among Black and Hispanic voters. In that regard, protest votes in the Democratic primary offered some mixed signals.

There was little indication that the “uncommitted” movement around the Gaza war spread significantly beyond the young voters and Arab American communities where it was strongest.

In Michigan, where the “uncommitted” campaign was perhaps most prominent, Biden performed especially well in predominantly Black precincts.

But there were voters casting ballots against Biden for other reasons, too.

In Texas, non-Biden candidates got more than 30 percent of the vote in half a dozen border counties. (The state doesn’t have an “uncommitted” option.) And the incumbent president failed to crack 50 percent in Zapata and Starr counties, a continuation of a troubling trend of waning support for Democrats in the region.

The bright side for Biden is that, at least in the primary, the pattern from South Texas did not seem to replicate in other majority-Hispanic counties or border communities. Biden put up a strong primary margin in the battleground state of Arizona, with Marianne Williamson — the wellness guru-turned presidential candidate who called for a ceasefire in Gaza — getting only a small share of the vote.

The “uncommitted” vote got a bit shy of 10 percent in New Mexico’s Tuesday primary, which was among the last places polls closed. Williamson came in around 6.7 percent.

Taken together, border counties in the state came in roughly in line with the statewide shares, although that was driven by a relatively strong performance for Biden in Doña Ana County, home to Las Cruces, while “uncommitted” hovered around 15 percent in a handful of less populous border counties.