A proposed $15-an-hour minimum wage for hospitality and transportation workers in SeaTac scored endorsements Tuesday from 20 elected Democrats, including U.S. Rep. Adam Smith, King County Executive Dow Constantine and state House Speaker Frank Chopp.

The endorsements were announced by Yes! For SeaTac, a union-backed political committee supporting the Nov. 5 ballot initiative.

Smith, a moderate Democrat who represents the 9th Congressional District, which stretches from his Tacoma neighborhood to Seattle’s Rainier Beach and Mercer Island, recalled growing up in the SeaTac area as the son of a ramp worker for United Airlines.

He said his father received “decent” wages and benefits, and “that enabled me to pursue my hopes and dreams.”

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“I’m very worried that we’re losing that,” he said in the prepared statement.

Other Democratic supporters include King County Council member Julia Patterson, a lifelong SeaTac resident; state Sen. Karen Keiser, of Kent; and state Reps. Dave Upthegrove and Tina Orwall, both from Des Moines.

SeaTac Proposition 1 calls for a $15-an-hour “living wage” for hospitality and transportation workers in and around Sea-Tac International Airport.

The measure also requires airport-related employers to provide paid sick leave and to offer jobs to part-time workers before hiring new full-time employees. If an affected business is sold, the new owner would have to keep existing employees for at least 90 days. Those requirements can be waived if a business agrees to a collective bargaining agreement with a union.

The so-called Good Jobs Initiative is opposed by Alaska Airlines and other affected businesses, including hotels, car-rental companies and restaurants. They argue that under the proposal, employers would be less likely to hire young, inexperienced workers, and local taxpayer money would be diverted away from things like public safety to cover the law’s enforcement costs.

Common Sense SeaTac, a business-funded political-action committee, has raised more than $275,000 to defeat the measure, according to reports filed with the state Public Disclosure Commission.

Meanwhile, Yes! for SeaTac has raised more than $343,000 in cash and in-kind donations.

Amy Martinez: 206-464-2923 or amartinez@seattletimes.com. On Twitter: @amyemartinez