Democratic presidential hopefuls are seizing on anti-corporate rhetoric and policy proposals as they look to win the support of influential labor unions and frame themselves as working-class heroes.

While virtually every Democrat in the race has sworn off corporate campaign cash, many are still grappling with past ties to powerful industries and fear that candidates like Sen. Bernie Sanders Bernie SandersOutrage erupts over Breonna Taylor grand jury ruling Dimon: Wealth tax 'almost impossible to do' Grand jury charges no officers in Breonna Taylor death MORE (I-Vt.) could eventually frame their more recent denunciations of big business and special interests as inauthentic or opportunistic.

Sen. Elizabeth Warren Elizabeth WarrenDimon: Wealth tax 'almost impossible to do' CNN's Don Lemon: 'Blow up the entire system' remark taken out of context Democrats shoot down talk of expanding Supreme Court MORE (D-Mass.), a longtime critic of big business who has called for the break-up of big tech companies like Amazon, has been especially vocal. She recently joined Stop & Shop workers on strike in Somerville, Mass, on April 12, the day after the strike for better wages and benefits was declared.

Stop and Shop "workers deserve fair wages and good benefits—and I’m behind them 100% of the way," she tweeted last week.

"I stand in solidarity with @UFCW and the 31K workers who are making their voices heard," she added, referring to the United Food and Commercial Workers International Union.

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South Bend, Ind., Mayor Pete Buttigieg Pete ButtigiegThe Hill's Morning Report - Sponsored by Facebook - GOP closes ranks to fill SCOTUS vacancy by November Buttigieg stands in as Pence for Harris's debate practice Hillicon Valley: FBI, DHS warn that foreign hackers will likely spread disinformation around election results | Social media platforms put muscle into National Voter Registration Day | Trump to meet with Republican state officials on tech liability shield MORE rallied with them on Friday in Malden, Mass. Former Vice President Joe Biden Joe BidenBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Democratic groups using Bloomberg money to launch M in Spanish language ads in Florida Harris faces pivotal moment with Supreme Court battle MORE, who has not officially declared his candidacy, rallied with the workers in Boston on Thursday. And Sen. Amy Klobuchar Amy KlobucharSocial media platforms put muscle into National Voter Registration Day Battle lines drawn on precedent in Supreme Court fight Sunday shows - Ruth Bader Ginsburg's death dominates MORE (D-Minn.) joined them on the picket line on Friday in Somerville.

Additionally, Sens. Cory Booker Cory Anthony BookerBipartisan praise pours in after Ginsburg's death DHS opens probe into allegations at Georgia ICE facility Democratic lawmakers call for an investigation into allegations of medical neglect at Georgia ICE facility MORE (D-N.J.), Kamala Harris Kamala HarrisHarris faces pivotal moment with Supreme Court battle Nearly 40 Democratic senators call for climate change questions in debates Joe Biden has long forgotten North Carolina: Today's visit is too late MORE (D-Calif.) and Kirsten Gillibrand Kirsten GillibrandSunday shows preview: Justice Ginsburg dies, sparking partisan battle over vacancy before election Suburban moms are going to decide the 2020 election Jon Stewart urges Congress to help veterans exposed to burn pits MORE (D-N.Y.) tweeted their support for the strike.

Sanders, who has made income inequality and protecting workers a key part of his campaign, has repeatedly touted his support for unions and his denunciations of "corporate greed."

"We need elected officials and candidates at every level to get serious about forcefully speaking out for unions. It’s not good enough for candidates to say they like “workers” or the “middle class.” We need to specifically and explicitly support trade UNIONS," Sanders tweeted earlier this month.

No candidate “wants to be the last one to the table” when it comes to working-class issues, one Democratic source in New Hampshire said, noting that while Sanders carried that mantle in 2016, other 2020 hopefuls have taken up similar positions.

For some candidates, the anti-corporate messaging appears intended to reassure voters that they have come to embrace a more progressive platform – and that past industry ties will not influence their campaigns.

Booker, for instance, has sought to overcome criticism that he is too cozy with corporate interests, including those of the pharmaceutical industry.

In a radio interview in February, the New Jersey senator said that, if elected president, he would hold to account drug companies that hike price excessively.

“It’s unconscionable how people are profiteering off the pain of others, and we’re going to make sure we hold them accountable,” he said.

The anti-corporate, pro-labor message is reflective of a sense among some Democrats that the party has drifted away from its working-class reputation in recent years, ultimately ceding the industrial-era hubs that Democrats once relied on – Wisconsin, Michigan and Pennsylvania among them – to President Trump Donald John TrumpBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Romney: 'Unthinkable and unacceptable' to not commit to peaceful transition of power Two Louisville police officers shot amid Breonna Taylor grand jury protests MORE in 2016.

That notion has been seared into Democrats’ 2020 strategies: virtually every candidate vying for the Democratic nomination has denounced the role of corporate money in politics; campaign rhetoric is rife with tales of blue-collar upbringings and life experiences; and talking about corporate greed has become a crowd-pleaser at rallies.

Candidates like Rep. Tim Ryan Timothy (Tim) RyanNow's the time to make 'Social Emotional Learning' a national priority Mourners gather outside Supreme Court after passing of Ruth Bader Ginsburg Lincoln Project hits Trump for criticizing Goodyear, 'an American company' MORE (D-Ohio), for example, have made their working class backgrounds a key part of their campaigns, often in personal terms.

In his announcement, Ryan recounted how his father-in-law was laid off from Youngstown Sheet and Tube in the late 1970s and, later, how jobs at a local factory in Ohio were offshored to China.

Steven Billet, the director of the masters program in legislative affairs at George Washington University, said candidates joining workers on strike so they can’t get pinned as the pro-big business politician in the race is “a rational strategy.”

“This element of the Democratic Party is probably its most active and vocal. A full-blown attack by them could cripple some of the weaker campaigns,” Billet told The Hill. “With the large number of candidates in the field, voters are looking for any reason/any weakness to eliminate candidates from the field.”

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He added that staking out a position with this element inoculates a candidate from subsequent attacks related to their "purity."

By talking up their working-class credentials, Democrats are also hoping to score endorsements from organized labor.

Many unions are waiting longer to endorse in the 2020 race, fearing a repeat of 2016. That year, several labor groups saw local and regional chapters endorse Sanders despite national leaders offering their support to Hillary Clinton Hillary Diane Rodham ClintonDemocratic groups using Bloomberg money to launch M in Spanish language ads in Florida The Hill's Campaign Report: Presidential polls tighten weeks out from Election Day More than 50 Latino faith leaders endorse Biden MORE.

The delayed endorsements have not stopped candidates from meeting with labor leaders, speaking at union conferences and picketing with workers.

Just this month, for instance, more than half a dozen Democratic contenders spoke at the North America’s Building Trades Unions legislative conference in Washington.

There are also financial incentives for courting organized labor. Some unions have associated political action committees (PACs) that can dole out valuable campaign dollars to candidates.

Harris, for example received $1,000 from the San Francisco-based International Longshore & Warehouse Union Political Action Fund just last month, though other candidates, like Warren, have disavowed PAC contributions entirely, not just those from corporate-aligned groups.

Ultimately, candidates hope that support for unions will translate into good will - and votes - during the primary process.

Shortly after Buttigieg appeared with striking UFCW workers, the union, which has nearly 1.3 million members spread across the United States and Canada, expressed its gratitude.