On a Saturday evening in Michigan, the skies still hazy from drifting Canadian wildfire smoke, hundreds of voters packed into Detroit's opulent 104-year-old Opera House, rising from their seats to cheer loudly as Senator Bernie Sanders and Democratic Representative Alexandra Ocasio-Cortez took the stage.

As two of the leading figures on the American left, Ocasio-Cortez and Sanders were there to champion Senate hopeful Abdul El-Sayed – a doctor running on a platform of universal healthcare.

His supporters carried signs with El-Sayed's slogan "Medicare for All", and wore shirts urging the end of immigration enforcement and US aid to Israel.

But they were not the only ones tuning in.

Voters and politicians across the country are watching to see if El-Sayed can earn the Democratic nomination to run for Senate in November's midterm elections. His opponent – Congresswoman Haley Stevens – is an experienced politician with deep pockets, thanks in part to large corporate campaign donations.

The two represent the divisions within the Democratic Party as it seeks to take back control of Congress. On one side is the centrist establishment, backed by traditional power players. On the other is the left wing of the party, exemplified by Sanders and Ocasio-Cortez as well as New York City Mayor Zohran Mamdani.

But while left-wing Democrats have seen a wave of victories during this summer's primaries – including in New York and Colorado – what remains to be seen is if they can claw back support from disillusioned working-class voters, who flocked to President Donald Trump in 2024.

In Michigan – which voted for Democrat Joe Biden in 2020 but Trump four years later – the open Senate seat is a must-win for Democrats.

The seat had been held by one of their own, and if the party hopes to make gains in the Senate, and halt Trump's agenda, they will need to keep a hold of it. Whoever wins the primary on 4 August will be competing against Trump ally Mike Rogers come 3 November.

At Saturday's rally, some in the crowd felt hopeful, as Ocasio-Cortez promised El-Sayed represented the "politics of the future".

But miles outside the venue, other voters were less certain of his ability to beat Stevens – or to secure a victory for the Democrats by touting policies like healthcare for all and staunch opposition to Israel's military campaign in Gaza.

"This may not be the moment for progressives," said Colleen Houlihan, a 74-year-old from Ferndale, Michigan who is likely voting for Stevens. "I want radical change in the country, but we've got to start with this administration and it's got to be an electable candidate to get power back in sane hands."

El-Sayed is locked in a tight race against Stevens, a moderate Democrat who has pitched herself as the more experienced congresswoman and earned the endorsement of Michigan's governor Gretchen Whitmer as well as outgoing Senator Gary Peters.

It is not the only test of progressive power in a midwestern battleground state, as self-described Democratic socialist Francesca Hong attempts to secure a win in the governor's race in neighbouring Wisconsin just a week later.

Some political experts and voters questioned whether the current momentum would be enough to win over voters in the politically diverse, and historically working-class, midwest.

"They got a big win electing Mamdani mayor of New York City, but also, it's New York City," said Adrian Hemond, a political strategist in Michigan. "They have been much less able to win in some more traditionally purple areas."

On a humid morning before Saturday's rally, Corie Johnson was knocking on voters' doors for the first time in her life. The 35-year-old has always voted for Democrats, but said El-Sayed is the first candidate she has felt excited about.

"We're not so stuck in our ways," she said of millennial voters. "I think that's why he's gaining so much momentum."

Walking by the rowhouses on the streets of Hamtramck, a small town within Detroit, Johnson and her fellow canvassers were attempting to carry on a pitch they had heard from El-Sayed in a meeting just moments before.

"Money out of politics, money in pockets, Medicare for all," El-Sayed and his group of volunteers chanted together in the campaign's Detroit office.

The former Wayne County health director's policy plans – including universal healthcare and an annual wealth tax on billionaires – represent a pivot for a Democratic Party that has seen one of its lowest favourability ratings in recent years. In 2025, the number of Democrats who viewed their own party positively fell by 12% to 67%, according to a Gallup poll, external.

Despite his left-wing stances, El-Sayed has avoided the label claimed by many of his peers: Democratic socialist. But he is still taking lessons from their wins, especially Mamdani, whose social media skills and laser focus on affordability helped propel him to victory in New York.

El-Sayed's affordability platform – including his focus on health insurance – is why Les Lukacs of Monroe, Michigan, is voting for him. The longstanding Democrat who does not have health insurance said he would not vote for Stevens in November if El-Sayed lost the primary.

"We can barely afford groceries and gas," he said. "I have to make sacrifices – and healthcare is one of them."

Polling from the last year suggests healthcare costs remain among the top issues for voters in the November midterms, alongside the rising cost of gas, groceries and housing.

El-Sayed told the BBC that if the Democratic Party had more concerns for everyday people, "they'd be fighting on the same policies I'm fighting for".

In a statement to the BBC, a spokesperson for Stevens' campaign said the congresswoman would "fight for all Michiganders from every zip code to lower costs, protect manufacturing jobs, and take on Donald Trump's corruption and abuses of power".

Following in the footsteps of his peers on the left of his party, El-Sayed has spoken out against US involvement in the Middle East, including aid to Israel. Recent polling suggests a growing portion of voters believe the US is too supportive of its longtime ally in the wake of the war.

The issue has particular resonance in Michigan, which is home to the second largest Arab-American population in the US.

El-Sayed – the son of Egyptian immigrants – has called Israel's actions in Gaza a genocide. He has also been quick to invoke his opponent's ties to AIPAC (the American Israel Public Affairs Committee), which has spent almost $30m to back Stevens in the race.

Like many more moderate Democrats, Stevens has said she supports upholding US aid to Israel without conditions. She did not respond to a request for comment from the BBC on her stance on Israel.

Rex Nazarko, the leader of the American Muslim Engagement and Empowerment Network, believes El-Sayed will pick up some of the thousands of Democrats in the state who chose not to support Kamala Harris and Joe Biden in the 2024 presidential election because of their stance on Israel.

Cedric Erkins, a sheriff's deputy in Auburn Hills, Michigan, who has not decided his vote, is frustrated by costs skyrocketing in the US, while the country "can afford to send billions overseas".

While the Democratic Party has been mostly united against Trump's war in Iran, the Israel-Gaza war continues to present a dilemma for Democrats, who have historically depended on votes from both the Jewish and Arab communities to win elections, said Larry Sabato, the director of the University of Virginia Center for Politics

"They have to make a choice," he said. "Both sides are trying to make it as painful as possible."

As some left-wing voters rally behind El-Sayed, other Democrats remain worried about whether the movement is popular enough to help Democrats win back swing states.

Sally, a 45-year-old Michigan resident who declined to share her last name because she is an elected official, said she was excited by the movement's enthusiasm, but wasn't sure it was sustainable.

"There's a lot of that momentum, but keeping that momentum going is really hard," she said.

She added that even though Stevens had been attacked for her ties to corporate campaign funding, big money helps in politics.

"It's those connections that are going to support changes in law and make things move faster," she said.

Some of El-Sayed's voters, steadfast in their support, also worried whether their votes would be enough.

"I'm a little scared. I'm a little nervous," said Claire McHugh, a 70-year-old who went to the rally. "I just hope that enough people are fed up with the status quo."

Asked whether he believed left-wing candidates could win over more moderate Democrats to beat Republicans, El-Sayed told the BBC that he was not concerned with the future of the Democratic Party.

But, he added, "If Democrats want to find their future, I think we're showing it to them right here."

Sabato said it remained to be seen which faction of the Democratic Party would prevail.

But regardless, he said, Democrats would have to find a way to "sew these two very large groups back together" if they wanted to reverse recent election losses.

"It's already frayed," he said. "If they don't do the repair job they need to do and quickly, certainly through 2028, then they're going to have to get used to losing."