New York City’s social services agency now runs one of the nation’s largest housing assistance programs, according to new city data, but advocates and one mayoral candidate say it could be even bigger. The city’s voucher program is growing in importance, Social Services Commissioner Molly Wasow Park said. “It’s a big financial commitment.”CityFHEPS has played a key role for the bulk of the people who were moving out of shelters into permanent housing. Still, the number of New Yorkers staying each night in city shelters, including recently arrived immigrants ineligible for government housing aid, remains near record highs amid a deep housing shortage. Rosario said he is working side jobs to earn enough to pay for housing without assistance, but the voucher has given him breathing room.