NEW YORK — As the primary race for New York City mayor heads into the final 10 weeks, a left-leaning group — buoyed by a new poll showing popularity for its chief policy goals — is gearing up to make a public case against frontrunner Andrew Yang. The political action committee “Our City” recently commissioned a survey that found 56 percent of likely voters are unsure who to back in the eight-way Democratic primary — a race Yang has dominated since his entry in January. But the same 509 voters said they are looking for a candidate committed to shifting resources away from the NYPD, expanding affordable housing and increasing taxes on high earners to underwrite the city’s recovery from Covid-19.