WASHINGTON (AP) — While Joe Biden and Donald Trump are marching toward their respective presidential nominations, Michigan’s primary on Tuesday could reveal significant political perils for both of them.

Trump, despite his undoubted dominance of the Republican contests this year, is facing a bloc of stubbornly persistent GOP voters who favor his lone remaining rival, former U.N. Ambassador Nikki Haley, and who are skeptical at best about the former president’s prospects in a rematch against Biden.

As for the incumbent president, Biden is confronting perhaps his most potent electoral obstacle yet: an energized movement of disillusioned voters upset with his handling of the war in Gaza and a relationship with Israeli Prime Minister Benjamin Netanyahu that critics say has been too supportive.

Those dynamics will be put to the test in Michigan, the last major primary state before Super Tuesday and a critical swing state in November’s general election. Even if they post dominant victories as expected on Tuesday, both campaigns will be looking at the margins for signs of weakness in a state that went for Biden by just 3 percentage points last time.

Biden said in a local Michigan radio interview Monday that it would be “one of the five states” that would determine the winner in November.

Michigan has the largest concentration of Arab Americans in the nation, and more than 310,000 residents are of Middle Eastern or North African ancestry. Nearly half of Dearborn’s roughly 110,000 residents claim Arab ancestry.

It has become the epicenter of Democratic discontent with the White House’s actions in the Israel-Hamas war, now nearly five months old, following Hamas’ deadly Oct. 7 attack and kidnapping of more than 200 hostages. Israel has bombarded much of Gaza in response, killing nearly 30,000 people, two-thirds of them women and children, according to Palestinian figures.

Democrats angry that Biden has supported Israel’s offensive and resisted calls for a ceasefire are rallying voters on Tuesday to instead select “uncommitted.”

The “uncommitted” effort, which began in earnest just a few weeks ago, has been backed by officials such as Democratic Rep. Rashida Tlaib, the first Palestinian-American woman in Congress, and former Rep. Andy Levin, who lost a Democratic primary two years ago after pro-Israel groups spent more than $4 million to defeat him.

Abbas Alawieh, spokesperson for the Listen to Michigan campaign that has been rallying for the “uncommitted” campaign, said the effort is a “way for us to vote for a ceasefire, a way for us to vote for peace and a way for us to vote against war.”

Trump won the state by just 11,000 votes in 2016 over Democratic candidate Hillary Clinton, and then lost the state four years later by nearly 154,000 votes to Biden. Alawieh said the “uncommitted” effort wants to show that they have at least the number of votes that were Trump’s margin of victory in 2016, to demonstrate how influential that bloc can be.

“The situation in Gaza is top of mind for a lot of people here,” Alawieh said. “President Biden is failing to provide voters for whom the war crimes that are being inflicted by our U.S. taxpayer dollars – he’s failing to provide them with something to vote for.”

Our Revolution, the organizing group once tied to Sen. Bernie Sanders, I-Vt., has also urged progressive voters to choose “uncommitted” on Tuesday, saying it would send a message to Biden to “change course NOW on Gaza or else risk losing Michigan to Trump in November.”

Rep. Ro Khanna, D-Calif., a Biden backer who held several meetings and listening sessions in Michigan late last week, said he told community members that, despite his disagreements over the war, he would nonetheless support Biden because he represents a much better chance of peace in the Middle East than Trump.

“I also said that I admire those who are using their ballot in a quintessentially American way to bring about a change in policy,” Khanna said Monday, adding that Biden supporters need to proactively engage with the uncommitted voters to try and “earn back their trust.”

“The worst thing we can do is try to shame them or try to downplay their efforts,” he said.

Trump has drawn enthusiastic crowds at most of his rallies, including a Feb. 17 rally outside Detroit drawing more than 2,000 people who packed into a frigid airplane hangar.

But data from AP VoteCast, a series of surveys of Republican voters in Iowa, New Hampshire and South Carolina, reveals that his core voters so far are overwhelmingly white, mostly older than 50 and generally without a college degree. He will likely have to appeal to a far more diverse group of voters in November. And he has underperformed his statewide results in suburban areas that are critical in states like Michigan.

Several of Trump’s favored picks in Michigan’s 2022 midterm contests lost their campaigns, further underscoring his loss of political influence in the state. Meanwhile, the state GOP has been riven with divisions among various pro-Trump factions, potentially weakening its power at a time when Michigan Republicans are trying to lay the groundwork to defeat Biden this fall.

Both Biden and Trump have so far dominated their respective primary bids. Biden has sailed to wins in South Carolina, Nevada and New Hampshire, with the latter victory coming in through a write-in campaign. Trump has swept all the early state contests and his team is hoping to lock up the delegates needed to secure the Republican nomination by mid-March.

Nonetheless, an undeterred Haley has promised to continue her longshot presidential primary campaign through at least Super Tuesday on March 5, when 15 states and one territory hold their nominating contests.

As Haley stumped across Michigan on Sunday and Monday, voters showing up to her events expressed enthusiasm for her in Tuesday’s primary — even though, given her losses in the year’s first four states, it seemed increasingly likely she wouldn’t win the nomination.

“She seems honorable,” said Rita Lazdins, a retired microbiologist from Grand Haven, Michigan, who in an interview Monday refused to say Trump’s name. “Honorable is not what that other person is. I hate to say that, but it’s so true.”

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Associated Press writers Meg Kinnard in Grand Rapids, Michigan, and Joey Cappelletti in Lansing, Michigan, contributed to this report.