Mayor Bill de Blasio plans to rally volunteers, knock on doors and make phone calls to voters during a trip to Iowa for his onetime boss Hillary Clinton in her final days before the state’s caucus.

De Blasio will be joined by his wife, Chirlane McCray, as they seek to help Clinton defeat U.S. Sen. Bernie Sanders of Vermont for the Democratic presidential nomination, according to de Blasio’s political team.

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The couple will pay their own way, with a portion possibly being reimbursed by Clinton’s campaign, said de Blasio spokesman Dan Levitan. The trip begins Friday and ends the day after Monday’s caucus.

The itinerary is incomplete, but the plan is to be in Des Moines on Saturday.

De Blasio will travel with aides, who will pay for their own trips, his team said. Inquiries to the NYPD about who’s covering expenses of the mayor’s police bodyguards were unanswered.

De Blasio had withheld his endorsement of Clinton for months after most of the New York Democratic establishment bestowed its nod, saying he said he wanted to hear more about how the former first lady and secretary of state planned to narrow income inequality. He endorsed her in October.

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Clinton, 68, finds herself in an unexpectedly tight race with Sanders, 74, a left-leaning senator from Vermont.