SEATTLE — Seattle voters appear to support a new property tax to support free preschool for low-income 3- and 4-year-olds.

In the first 100,000 votes counted in King County on Tuesday, voters were giving an enthusiastic endorsement to Proposition IB, which would establish a new property tax that would pay for a pilot program for free and reduced-cost preschool.

A competing preschool proposal supported by labor unions, Proposition IA, appeared to be losing to the city council-supported plan.

Proposition IA would have taken money out of the city’s existing budget to pay for teacher training and a study on how to make preschool more affordable for all.

Mayor Ed Murray declared victory for the new preschool tax, calling it a huge win for Seattle kids.

The other side vowed to work with the city no matter what the vote tally shows.

Karen Hart, president of Service Employees International Union 925, said preschool teachers across Seattle are ready to work with the city to support whichever proposal passes.

“Tonight the only thing we know for sure is that two good ideas to improve early education for young children, Propositions 1A and 1B, cannot both pass,” Hart said.

She repeated the campaign’s complaint that the city did not allow voters the chance to vote yes on both proposals, which they considered complimentary.