David O'Keeffe is 27 years old and in both of the past two presidential elections -- spanning the entire time he could cast a ballot -- he's been voting against Donald Trump rather than for Trump's challenger, he says.

"Never in my life have I voted in a presidential general election for a candidate who aligns with my political agenda and how I see our country solving our biggest problems," he told ABC News in a recent interview.

This year, he has a new focus: mobilizing potential Democratic voters to cast ballots against President Joe Biden during the primary process in opposition to Biden's policies on the Israel-Hamas war in Gaza, sparked by Hamas' Oct. 7 terror attack.

Over the past month, O'Keeffe has been organizing with Listen to Wisconsin through the Democratic Socialists of America. They're one of several groups that are urging voters to pick "uninstructed" in the Democratic primary on Tuesday.

O'Keeffe says he sees the protest as a wake-up call.

The results from Tuesday will also be closely watched for signs of how potent the war remains as a political issue among some Biden-leaning voters whom he can't afford to lose in a close election this fall.

Advocates hope to bend his views on the conflict, pushing him closer, vote by vote, toward endorsing an end to the fighting.

"Biden previously did a lot of work in 2020 to keep the left and the Democratic coalition strong and together, and instead he's casting aside young voters, voters of color," O'Keeffe argued. "Good elected officials don't push the coalition away. That's not how we won in 2020 and the Democrats are sleepwalking into a loss in November."

The uninstructed push is an offshoot of a similar campaign backing "uncommitted" votes in Michigan, Minnesota, North Carolina and Washington state.

Those efforts have seen some relative success -- uncommitted has won 25 delegates so far, compared to Biden's 2,600-plus, according to ABC News' count; and uncommitted got about 20% of the vote in Minnesota.

Uncommitted organizers previously pledged to continue urging protest votes over the war in various states around the country.

Wisconsin, like Michigan, has particular political significance. It's part of the critical "blue wall" in the Midwest that had voted Democratic for decades before Donald Trump's candidacy. Biden only won the state over Trump in 2020 by some 20,000 votes. A loss in November would likely be a major blow to his reelection plans.

His campaign is not ignoring the protest efforts over the war.

Asked by ABC News about how they're handling the uninstructed vote, Biden spokesperson Lauren Hitt echoed what he has said on the trail himself -- that he is "working tirelessly" to put an end to the violence.

"The President believes making your voice heard and participating in our democracy is fundamental to who we are as Americans. He shares the goal for an end to the violence and a just, lasting peace in the Middle East," she said.

More broadly, popular opinion about Israel's response has also begun to fade, polling shows: According to a Gallup survey conducted in March, approval among Americans of Israeli military action in Gaza dropped to 36%.

Biden has tried to balance his support for Israel's campaign against Hamas with sympathy for the more than 32,000 people who have been killed, according to the Hamas-run health ministry in Gaza, amid Israel's bombardment of the Palestinian territory.

The president has pushed for negotiations to implement temporary cease-fires in exchange for hostage releases and criticized Israel's tactics as "over the top." But he has not said he would condition aid to the country on an end to Israel's retaliation or on negotiations with the Palestinians, and he has been criticized in the past for some of his rhetoric about the death toll.

Biden privately met with some advocates. He's become increasingly vocal about his disagreements with Israel's strategy.

At a recent fundraiser in New York City, the program was interrupted at least six times over the war in Gaza. When asked about it by host Stephen Colbert, Biden advocated for a two-state solution for Israel and the Palestinians and emphasized that Israel "must" stop any "effort resulting in significant deaths of innocent civilians."

But that isn't enough, his critics contend.

O'Keeffe told ABC News that he fears another Trump presidency and he hopes to be able to vote for Biden in November if Biden calls for an immediate, permanent cease-fire, though Israeli officials maintain that Hamas' fighting capabilities must be dismantled to prevent future attacks.

"We want to see policy change now on this issue, so that people can believe voting for a Democrat means something," O'Keeffe said.

Uninstructed not a permanent vote against Biden, supporters say

It's Ramadan, the holiest month in Islam, which requires Muslims to fast from dawn to sunset.

On a recent Friday evening in Milwaukee, Heba Mohammad, a Palestinian American and the former digital organizing director of Biden's 2020 Wisconsin campaign, hosted an iftar, or sunset meal. Around 150 Muslims and allies of the Listen to Wisconsin movement filed into the theater to break their fast.

Like O'Keeffe, Mohammad said she was tired of campaigning against a candidate rather than for them. She told ABC News that it's easier mobilizing for "uninstructed" right now than it was organizing for Biden in 2020.

"The overwhelming sense was that people were voting because they were scared of Trump and that's why they were voting for Biden. This movement is giving people something to believe in and to vote for and organize for, which is a huge distinction to me," Mohammad said.

Jim Morgan and his wife, Sally, aren't Muslim or Arab but their daughter-in-law is Palestinian. They attended the Milwaukee gathering out of solidarity and frustration with the Biden administration's handling of the war in Gaza, they said.

They're both committed to voting for Biden in November to stop Trump -- but they plan on voting "uninstructed" to gain his "attention" during the primary.

"I think by voting 'uninstructed' or 'uncommitted' like the other states are, [Biden] will realize that a lot of his base support is displeased. He needs to be bolder. We need a cease-fire," Sally Morgan said.

'I feel like they use us a lot'

Arab American and Muslim voices have been at the forefront of some of the criticism of Biden's handling of the war. But in Wisconsin, there are other dynamics.

Justin Blake's nephew Jacob Blake, a Black man, was shot in the back seven times by the police in Kenosha, Wisconsin and left partially paralyzed -- a notorious incident captured on camera.

Justin Blake helped organize for Black Lives Matter and, in turn, campaign for Biden in 2020. But this year he's come down from Chicago to help organize for uninstructed.

At an event on Saturday in Milwaukee he told ABC News it was important to emphasize the similarities between the Black community and the Palestinians, both of whom he said need "liberation."

As the demonstrators passed by an "I can't breathe" mural, a tribute to the mass protests around the country against racial injustice and police brutality in 2020, some Black attendees said they supported the uninstructed campaign for more reasons than the war in Gaza.

They felt Biden hadn't delivered on the promises he made to their communities in 2020, they said.

Some of the issues mentioned include health care, a stagnating minimum wage and roads so littered with potholes that they're nearly impossible to drive on.

Biden's defenders note that these issues aren't all within his power to address. About half of the country has raised its minimum wage, but in Wisconsin it remains at the federal minimum of $7.25 and state lawmakers have not been enthusiastic about an increase.

And though one of Biden's campaign promises was to raise the federal minimum wage to $15, he was only able to achieve this goal for federal workers because of resistance from some Democrats. He has, however, touted other bipartisan successes including infrastructure investment.

Shanice Jones, who has been out canvassing in Milwaukee for the group Black Leaders Organizing for the Community, or BLOC, said that as a mother, the images coming from Gaza deeply affected he. But she's also "tired" of supporting presidential candidates who don't support her community.

"I feel like they use us a lot, and we are tired of it. We gotta get out here. All the time knocking on doors, talking to people about voting ... It saddens me to hear people saying, 'Oh, I'm not voting. They never do nothing for us no way,'" Jones said. But, she added, "It's their fault people feel like that."

Referring to Biden directly, she added: "I feel like everybody deserves a chance once they get that chance, but it's up to what you do when you get to office to prove if you deserve another chance. And right now, the way he's going, I really don't feel like he should."

Biden's approval rating has consistently been the highest with Black Americans, among various groups, but that has eroded over time: According to a poll by the Associated Press and NORC Center for Public Affairs in December, "nationally, only 50% of Black adults said they approve of Biden, ... down from 86% in July 2021."

Sharon Kilfoy voted for Biden in 2020 and is neither Black, Muslim nor Arab. Outside of her home, filled with pieces of original art, are signs that read "Justice for Tony." Tony Robinson Jr. was an unarmed 19-year-old fatally shot by police in 2015 just down the street from her home. Kilfoy's grandchildren were friends with him, she said.

She, like Blake, sees parallels with how politicians are treating the war in Gaza and what's happened in her own backyard. She's not sure real change has been made.

Unusual among the voters that ABC News spoke with, Kilfoy had already heard of uninstructed by the time O'Keeffe and his colleague Gabo Ochoa Samoff had knocked on her door. But she hadn't yet committed.

She thanked the two of them for reminding her of the option and promised to go out and vote on Tuesday.

"I think sometimes we can be on the brink of change and have no awareness of it at all," she said. But "it's one thing when the political is in your mind. It's very different when it's in your heart, when it's in your stomach, when it's a kid that you've known."

ABC News' Juhi Doshi, Isabella Murray and Oren Oppenheim contributed to this report.