Michelle Obama, one of the Democratic Party’s most popular and elusive surrogates, will rally alongside Vice President Kamala Harris in Michigan on Saturday, making her return to the campaign trail less than two weeks before Election Day.

With the race against former President Donald J. Trump virtually deadlocked, the Harris campaign is deploying Mrs. Obama as part of a flurry of activity to mobilize voters to the polls. The former first lady has high approval ratings from groups of voters whom the Harris campaign is trying to reach in the final stretch of the election, including suburban and Black Americans.

On Saturday, Mrs. Obama is scheduled to visit Kalamazoo County, a moderately liberal, predominantly white slice of southwestern Michigan that is home to a subset of those voters: Michiganders who overwhelmingly chose Nikki Haley over Mr. Trump in the states’s Republican primary election. Ms. Harris is hoping to attract those voters and has aggressively courted moderate independents and Republicans, especially women.

Valerie Jarrett, a close friend to Mrs. Obama and a former senior adviser to President Barack Obama, said that Mrs. Obama had a “keen appreciation” for the job her husband had held and the one Ms. Harris is seeking, and would most likely use her time onstage to talk about the qualities she believes are important to the presidency. In her own speeches and media appearances, the vice president has spent time drawing a sharp character contrast between herself and Mr. Trump.

Mrs. Obama’s approach, Ms. Jarrett said, could appeal to some of the most coveted slices of voters across battleground states in the days ahead precisely because she is not a politician. Ms. Jarrett described Ms. Harris and Mrs. Obama as “friends” and said that the vice president had called the former first lady to seek her counsel, partly because she “has a good pulse” for what people outside conventional politics are saying and feeling about the race.

“I think many of us are so concerned about the acrimony and polarization and toxicity in the zeitgeist right now,” Ms. Jarrett said. “I think Michelle Obama uniquely can rise above that and appeal to our better angels.”

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