Boston mayoral candidate Josh Kraft says the city’s growing payroll, boasting more than 500 employees who earned more than $300,000 last year, is the “latest example” that more fiscal responsibility is needed at City Hall.

The survey offers the first early look at the matchup between the first-term progressive mayor and her most prominent challenger.

Boston’s largest police officers' union will endorse incumbent Mayor Michelle Wu for reelection on Thursday afternoon, its leadership said. The Boston Police Patrolmen’s Association said its members voted “overwhelmingly” to support Wu at the union’s most recent monthly meeting.

Michelle Wu holds a double-digit lead over philanthropist Josh Kraft in the race for Boston mayor, a new poll from Emerson College finds. The preliminary election to narrow the field down to two candidates is in September. The poll asked more than 600 registered voters who they would vote for if the election were held today.

Mayor Wu is both gearing up for a competitive race against Kraft and preparing to testify before Congress about Boston's "sanctuary" policies.

The endorsement is the first time in more than 30 years that the city's largest police union has supported a Boston mayor for reelection, the union said.