NEWARK — An Obama administration reunion tour is unfolding in New Jersey, as a cavalcade of Democratic luminaries has paraded into the state in recent days, including former Vice President Joseph R. Biden Jr., former Secretary of Labor Thomas E. Perez and former Secretary of State John Kerry, urging voters to make Philip D. Murphy, the Democratic candidate, their governor.

One by one, they have asked voters to treat the election for governor as a chance to preserve former President Barack Obama’s policies at the state level, even as they are under assault in Washington.

Mr. Obama himself is scheduled to appear with Mr. Murphy on Thursday at a rally in Newark, making his first public foray on the campaign trail in support of a Democratic candidate since leaving office. And Hillary Clinton will be a guest of honor at a closed-door fund-raiser for Mr. Murphy on Sunday in Harrison, N.J., her first campaign event since last year’s election.

The emphasis on a low-profile, off-year election for governor in New Jersey, where Mr. Murphy holds a commanding lead in recent polls to replace the Republican Chris Christie, reflects the Democratic Party’s changing priorities with it out of power in Washington. As the party has poured energy and money into contesting special elections for federal offices this year, elections for governor in New Jersey and Virginia — the only two statewide races in the country this year — offer Mr. Obama and his allies perhaps their best chance to protect policy achievements at the state level.

