PORTLAND – A lawmaker spearheading the fight for a single-payer health care system for Maine applauded Portland voters Wednesday for supporting the concept despite a television advertising blitz by the state’s largest health insurer.

But a spokesman for Anthem Blue Cross and Blue Shield said the insurer had no regrets about its expensive ad campaign and suggested that the outcome was more an expression of voter frustration with rising health care costs than of support for a Canadian-style system run by the state.

By a margin of 52 percent to 48 percent, residents of Maine’s largest city endorsed the idea of a single-payer plan that would guarantee coverage to everyone. The unofficial tally Tuesday was 6,979 in favor and 6,447 opposed.

Although the nonbinding measure makes no changes in the health care system, the vote was the first in Maine on the single-payer concept and came as the Health Security Board, a panel established this year by the Legislature, launched a study of the idea.

Rep. Paul Volenik, who introduced a single-payer bill in the Legislature and serves as co-chairman of the study panel, said the Portland vote was “absolutely critical” to the campaign and could set the stage for similar referendums elsewhere in the state.

“It showed that even the massive amounts of money put in by opponents were not enough to sway public opinion, which traditionally shows strong support for this issue,” said Volenik, D-Brooklin.

As of Oct. 25, referendum opponents raised more than $382,000, almost all of it from Anthem. Supporters reported contributions of less than $15,000.

Anthem spokesman Bill Cohen defended the advertising campaign and said it succeeded in eroding strong support for the referendum found in private polls early in the campaign.

“We started way in the hole and made up a huge amount of ground,” he said.

Cohen characterized Portland as “a very liberal community” and suggested that its views on the issue may not reflect those held elsewhere in the state.

Cohen said Anthem will work with the Health Security Board as it works on developing a framework for a single-payer plan. The 19-member board, made up of legislators, health care providers, state officials and representatives of the insurance industry and advocacy groups, is scheduled to report its findings by March 31.

“When you look at the board, it has a fair number of people who are already committed to single-payer. It is our hope and desire that the board will look at broad issues, not narrow issues,” Cohen said.

Volenik said the economic downturn is sure to have a bearing on the board’s deliberations. There would be less money available to finance a state-run system, he noted, but the need would be greater if more people wind up without health insurance coverage.

“These two factors are pulling in opposite directions and it’s hard to see how it will balance out,” he said.

Volenik said that once the Legislature gives its approval, the framework of a single-payer plan could be in place within six months or a year. He said that while uninsured Mainers could gain coverage quickly, there would be a two- or three-year transitional phase before others are brought into the state plan.

Volenik said that if the board presents a single-payer plan and the Legislature rejects it, the issue could go to a statewide referendum.

“The public may be incensed enough that they put it on the ballot themselves with a petition drive,” he said. “I could see that happening if we fail to act.”