DETROIT/WASHINGTON (Reuters) - Democratic presidential candidate Bernie Sanders is scheduled to join United Auto Workers members on a picket line in Detroit on Wednesday, underscoring the extent to which the longest auto worker strike in nearly 30 years has become a political event.

FILE PHOTO: Democratic U.S. presidential candidate Senator Elizabeth Warren attends the picket line with striking General Motors Detroit-Hamtramck Assembly plant workers during the United Auto Workers (UAW) national strike in Hamtramck, Michigan, U.S., September 22, 2019. REUTERS/Rebecca Cook/File Photo

The U.S. senator from Vermont, an independent, joins a parade of Democrats who have met with some of the 48,000 striking hourly workers, using the walkout against General Motors Co GM.N to amplify their messages about income inequality and corporate power. Their oratory comes on the heels of President Donald Trump's vows to protect U.S. manufacturing jobs with tariffs on imported cars, and his frequent criticism of GM for shutting UAW-represented factories in Ohio and Michigan.

GM workers went on strike on Sept. 16, seeking higher pay, greater job security, a bigger share of GM’s profit and protection of their healthcare benefits. Talks between the two sides continued on Tuesday.

The politicians’ appearances at plants throughout the Midwest over the past week emphasize the importance of the UAW to winning in states that will be pivotal to the 2020 presidential election.

In 2016, Republican Trump convinced numerous UAW members to vote for him, helping him win Michigan, Ohio and other states. The UAW has traditionally supported Democratic candidates. The union and its members contributed almost $16 million during the 2012 election cycle when former President Barack Obama was re-elected, making it one of the most politically active groups tracked by the nonpartisan Center for Responsive Politics. However, UAW contributions dropped to less than $5.8 million in 2016.

UAW workers gave Trump a higher than normal share of their votes in 2016 - 32% of the almost 400,000 members by the union’s reckoning.

“He is president because of this group of voters,” Harley Shaiken, labor professor at the University of California-Berkeley, said of blue-collar workers in the Midwest. “The strike has become a symbol for how the U.S. might compete in the global economy.”

UAW officials are not commenting publicly about the visits, but they are closely watching the 2020 candidates to see who is most involved with the strike effort as an audition for winning the union’s support.

On Sunday outside a GM plant in Kansas City, Kansas, Democratic presidential candidate Joe Biden said, “There used to be a basic deal in the old days. If you contributed to the welfare of the corporation you worked for, you got to share in the benefit ... That’s not the deal anymore.

“We didn’t bail out GM, the UAW bailed out GM,” he told the striking workers. “You gave up more than anybody. That’s why GM made it.”

In Detroit on the same day, U.S. Senator Elizabeth Warren, one of Biden’s rivals for the Democratic presidential nomination, credited unions with building the middle class in America, but said the middle class was now under attack.

“GM is demonstrating that it has no loyalty to the workers of America or to the people of America,” she told striking workers outside GM’s Detroit-Hamtramck assembly plant. “Their only loyalty is to their own bottom line and if they can save a nickel by moving a job to Mexico or to Asia or to anywhere else on this planet, they will do it.”

Other Democratic candidates who have visited striking workers include U.S. Senator Amy Klobuchar and U.S. Representative Tim Ryan. Former U.S. Representative Beto O’Rourke is visiting UAW members in West Chester, Ohio, on Tuesday and Lordstown, Ohio, on Wednesday.

GM REJECTS CRITICISM

The White House has said it is not involved in the talks, but Trump has repeatedly demanded GM find a new vehicle for its now-shuttered assembly plant in Lordstown. That region in the northeastern part of the state historically supported Democrats in presidential races but backed Trump in 2016.

Democratic candidates and labor leaders have blasted GM’s decision to stop paying healthcare benefits for striking UAW workers. The union’s strike fund is supposed to pay for coverage during a walkout.

GM officials have tried to counter charges that they are abandoning U.S. workers, releasing details of an offer to the UAW that included the promise of investing $7 billion in U.S. plants, annual raises in a new four-year deal, increased profit sharing and retention of existing healthcare insurance.

GM officials have expressed frustration with the attacks by the UAW and politicians on the company’s worker compensation.

“Criticism about the wages and benefits GM pays is unwarranted,” GM spokesman Jim Cain said on Tuesday. “The total compensation of our UAW workforce – including wages, profit sharing and benefits – is the highest in the U.S. auto industry.”

GM officials also privately say the decision on the health insurance was telegraphed well before the strike and no worker is without coverage thanks to the UAW strike fund.

Steven Bernstein, a management-side labor attorney from Tampa, Florida, said GM officials cannot afford to be drawn into a war of words.

“The best advice for management in circumstances like this is to make sure they don’t lose sight of their end objective,” he said.