"Today, I will in fact answer the president's call," Nutter said. "I will sign an executive order that gives Philadelphians a raise right now."
Cheers erupted in his reception room, where several minimum-wage workers and supporters of the move had gathered to watch the signing. Elsewhere, free-market-policy advocates said the move could harm the city.
Nutter's administration has not always favored imposing a minimum wage, and his action caught some by surprise, including activists who have pressed the issue for years. They noted that the May 20 primary ballot asks voters whether minimum-wage requirements should be extended to the city's subcontractors.
"While the mayor's executive order is commendable, it is not a replacement for ballot question No. 1, which would permanently apply the city's minimum wage standards to airport workers," said Gabe Morgan, state director of the SEIU 32BJ union.
The extension is effective May 20, the same day as the primary. First-tier subcontractors - those directly contracted by a company or group hired by the city for a particular job - will have to pay $10.88, the current minimum wage for city contractors.
Starting in January, all city contracts, including first-tier subcontractors, will have to increase wages to $12 hourly.
City Councilman W. Wilson Goode Jr., who sponsored the bill to put the question on the ballot, stood by Nutter as he signed the order. Goode called it "real help for real people."
Nathan A. Benefield, an analyst at the Commonwealth Foundation for Public Policy Alternatives, a think tank in Harrisburg, said minimum wage is a popular issue but warned that "there's always going to be trade-offs" - such as contractors hiring fewer people, and the city having to pay more in the end for contractors' work.
Nutter's own law department said last year that the City Charter does not give Council authority to force a wage standard on subcontractors. The administration initially voiced concern, too, about unintended consequences of such a standard.
But on Tuesday, Nutter said, "I finally came to the conclusion that . . . we cannot leave folks behind, and if people are doing better in the city, then we need to make sure some of that benefit is getting spread to those who needed it most."