Five days before Michigan holds a crucial primary in the race for the Democratic presidential nomination, Joe Biden has landed the backing of the state’s governor.

Democratic Gov. Gretchen Whitmer announced on Thursday that she is endorsing the former vice president, saying in a statement that “working families in Michigan need a president who will show up and fight for them, and Joe Biden has proven time and again that he has our backs.”

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Michigan is the largest and most important of the six states hold primaries next Tuesday, March 10.

The race for the Democratic nomination has essentially turned into a two-candidate battle between the establishment-backed Biden and Sen. Bernie Sanders of Vermont. The former vice president currently holds a slight edge over the populist lawmaker who describes himself as a democratic socialist in the all-important race for Democratic nominating convention delegates.

Whitmer – a former longtime state lawmaker -- emphasized that Biden’s “had all of our backs when he worked with President Obama to expand health care to millions of people under the Affordable Care Act, including 680,000 Michiganders who now have coverage through Medicaid expansion. He had our backs during the auto industry rescue that saved GM and Chrysler.”

The governor was named the fourth national campaign co-chair.

Sanders was the front-runner in the Democratic nomination race until Tuesday, when Biden caught up with him after sweeping 10 of the 14 states that voted on Super Tuesday. Other Democratic candidates – former New York City Mayor Mike Bloomberg, former South Bend, Ind. Mayor Pete Buttigieg, and Sen. Amy Klobuchar of Minnesota -- all ended their White House bids this week and endorsed Biden.

Sen. Elizabeth Warren, D-Mass., dropped out of the race on Thursday, but she has yet to endorse anyone.

Sanders - who’s making his second straight presidential run – defeated eventual nominee Hillary Clinton in the 2016 Democratic primary in the state, thanks to a last-minute upset win. That foreshadowed Clinton’s narrow loss to Donald Trump in the November 2016 general election in Michigan. Trump’s victory with working-class white voters in the state, as well as narrow wins in two other crucial Rust Belt states -- Pennsylvania and Wisconsin -- propelled him into the White House.

The latest poll in the state – Detroit News/WDIV-TV survey conducted before Biden’s big night on Super Tuesday – indicated the former vice president is topping Sanders by 6 percentage points.

With so much riding on the line in Michigan, Sanders on Thursday canceled a campaign stop scheduled for Friday in Mississippi -- another March 10th state - and instead said he would travel to Michigan.

"We are bringing more staff into Mississippi," he told reporters on Thursday.

But he emphasized that "Michigan is where we'll spend a bit of our time."

Sanders was swept by Biden in all five southern states that held primaries on Super Tuesday.